diff --git a/mapytex/calculus/API/expression.py b/mapytex/calculus/API/expression.py
index 335555d..b44953c 100644
--- a/mapytex/calculus/API/expression.py
+++ b/mapytex/calculus/API/expression.py
@@ -10,7 +10,7 @@
 Expression
 
 """
-from ..core import Tree, compute
+from ..core import Tree, compute, typing
 from .renders import renders
 
 class Expression(object):
@@ -104,9 +104,11 @@ class Expression(object):
         <Exp: 2 + 12>
         """
         try:
-            t = self._tree.apply_on_last_level(compute)
+            t = self._tree.apply_on_last_level(compute, typing)
         except AttributeError:
             return self
+        except NotImplementedError:
+            return self
         else:
             e = Expression(t, ancestor=self)
             return e.simplify()
diff --git a/mapytex/calculus/core/__init__.py b/mapytex/calculus/core/__init__.py
index 4f8c550..4028601 100644
--- a/mapytex/calculus/core/__init__.py
+++ b/mapytex/calculus/core/__init__.py
@@ -37,10 +37,8 @@ Abstracts tools for calculs manipulations
 >>> print(t.apply_on_last_level(compute, typing))
 +
  > /
- | > *
- | | > 2
- | | > 4
- | > 4
+ | > 2
+ | > 1
  > /
  | > 3
  | > 4
diff --git a/mapytex/calculus/core/compute/divide.py b/mapytex/calculus/core/compute/divide.py
index ec9afb7..7a81b44 100644
--- a/mapytex/calculus/core/compute/divide.py
+++ b/mapytex/calculus/core/compute/divide.py
@@ -10,6 +10,7 @@
 Divide MO
 """
 
+from decimal import Decimal
 from multipledispatch import Dispatcher
 from ..tree import Tree
 from ..MO.mo import MO, MOnumber
@@ -66,12 +67,22 @@ def divide_filter(left, right):
 def monumber_monumber(left, right):
     """ Divide 2 monumbers and return a MOFraction
 
+    >>> a = MOnumber(4)
+    >>> b = MOnumber(6.2)
+    >>> monumber_monumber(a, b)
+    Decimal('0.6451612903225806266768278939')
     >>> a = MOnumber(4)
     >>> b = MOnumber(6)
     >>> monumber_monumber(a, b)
-    <MOFraction 4 / 6>
+    Traceback (most recent call last):
+    ...
+    NotImplementedError: Can't divide 2 int. Need to create a Fraction instead
     """
-    return MOFraction(left, right)
+    if type(left.value) in [float, Decimal] or \
+            type(right.value) in [float, Decimal]:
+        return left / right
+    else:
+        raise NotImplementedError("Can't divide 2 int. Need to create a Fraction instead")
 
 @divide.register(MOnumber, MOFraction)
 @special_case(divide_filter)
diff --git a/mapytex/calculus/core/tree.py b/mapytex/calculus/core/tree.py
index 8e6d116..e84df16 100644
--- a/mapytex/calculus/core/tree.py
+++ b/mapytex/calculus/core/tree.py
@@ -294,10 +294,13 @@ class Tree(object):
 
         return Tree(self.node, left_applied, right_applied)
 
-    def apply_on_last_level(self, function):
+    def apply_on_last_level(self, 
+                            function, 
+                            type_function = lambda n,l,r: Tree(n,l,r)):
         """ Apply the function on last level of the tree before leaf
 
-        :param function: (op, a, a) -> b
+        :param function: (op, a, a) -> b function to apply on last level
+        :param type_function: (op, a, a) -> b  typing function to apply on subtree which raise a TypeError. The return value will be concidered as an leaf
         :returns: b if it is a 1 level Tree, Tree otherwise
 
 
@@ -325,22 +328,38 @@ class Tree(object):
         >>> print(ttt)
         14
         """
+
         left_is_leaf = 0
         right_is_leaf = 0
         try:
-            left_applied = self.left_value.apply_on_last_level(function)
+            left_applied = self.left_value.\
+                apply_on_last_level(function, type_function)
+        except NotImplementedError:
+            # TODO: overload __getitem__ to ease unpacking |dim. sept. 23 19:17:50 CEST 2018
+            left_is_leaf = 1
+            left_tree = self.left_value
+            left_applied = type_function(left_tree.node,
+                                         left_tree.left_value,
+                                         left_tree.right_value)
         except AttributeError:
             left_applied = self.left_value
             left_is_leaf = 1
 
         try:
-            right_applied = self.right_value.apply_on_last_level(function)
+            right_applied = self.right_value.\
+                apply_on_last_level(function, type_function)
+        except NotImplementedError:
+            right_is_leaf = 1
+            right_tree = self.right_value
+            right_applied = type_function(right_tree.node,
+                                         right_tree.left_value,
+                                         right_tree.right_value)
         except AttributeError:
             right_applied = self.right_value
             right_is_leaf = 1
 
         if left_is_leaf and right_is_leaf:
-            return function(self.node, self.left_value, self.right_value)
+            return function(self.node, left_applied, right_applied)
         else:
             return Tree(self.node, left_applied, right_applied)
 
diff --git a/mapytex/calculus/core/typing/__init__.py b/mapytex/calculus/core/typing/__init__.py
new file mode 100644
index 0000000..cd3eac4
--- /dev/null
+++ b/mapytex/calculus/core/typing/__init__.py
@@ -0,0 +1,44 @@
+#! /usr/bin/env python
+# -*- coding: utf-8 -*-
+# vim:fenc=utf-8
+#
+# Copyright © 2017 lafrite <lafrite@Poivre>
+#
+# Distributed under terms of the MIT license.
+
+"""
+Computing with MO
+"""
+
+from .exceptions import TypingError
+# from .add import add
+# from .minus import minus
+# from .multiply import multiply
+from .divide import divide
+
+OPERATIONS = {
+        # "+": add, 
+        # "-": minus, 
+        # "*": multiply,
+        "/": divide,
+        }
+
+def typing(node, left_v, right_v):
+    """ 
+    Typing a try base on his root node
+
+    :example:
+
+    >>> from ..MO.mo import MOnumber
+    """
+    try:
+        operation = OPERATIONS[node]
+    except KeyError:
+        raise TypingError(f"Unknown operation ({node})")
+    return operation(left_v, right_v)
+
+
+# -----------------------------
+# Reglages pour 'vim'
+# vim:set autoindent expandtab tabstop=4 shiftwidth=4:
+# cursor: 16 del
diff --git a/mapytex/calculus/core/typing/divide.py b/mapytex/calculus/core/typing/divide.py
new file mode 100644
index 0000000..c0d4567
--- /dev/null
+++ b/mapytex/calculus/core/typing/divide.py
@@ -0,0 +1,43 @@
+#! /usr/bin/env python
+# -*- coding: utf-8 -*-
+# vim:fenc=utf-8
+#
+# Copyright © 2017 lafrite <lafrite@Poivre>
+#
+# Distributed under terms of the MIT license.
+
+"""
+Typing trees with a divide root
+"""
+
+from multipledispatch import Dispatcher
+from ..MO.mo import MO, MOnumber
+from ..MO.fraction import MOFraction
+
+divide_doc = """ Typing trees a divide root
+
+:param left: left MO
+:param right: right MO
+:returns: Tree or MO
+
+"""
+
+divide = Dispatcher("divide", doc=divide_doc)
+
+@divide.register(MOnumber, MOnumber)
+def monumber_monumber(left, right):
+    """ A divide tree with 2 MOnumbers is a MOFraction
+
+    >>> a = MOnumber(4)
+    >>> b = MOnumber(6)
+    >>> monumber_monumber(a, b)
+    <MOFraction 4 / 6>
+
+    """
+    return MOFraction(left, right)
+
+
+# -----------------------------
+# Reglages pour 'vim'
+# vim:set autoindent expandtab tabstop=4 shiftwidth=4:
+# cursor: 16 del
diff --git a/mapytex/calculus/core/typing/exceptions.py b/mapytex/calculus/core/typing/exceptions.py
new file mode 100644
index 0000000..64efc60
--- /dev/null
+++ b/mapytex/calculus/core/typing/exceptions.py
@@ -0,0 +1,19 @@
+#! /usr/bin/env python
+# -*- coding: utf-8 -*-
+# vim:fenc=utf-8
+#
+# Copyright © 2017 lafrite <lafrite@Poivre>
+#
+# Distributed under terms of the MIT license.
+
+"""
+Exceptions for typing trees 
+"""
+
+class TypingError(Exception):
+    pass
+
+# -----------------------------
+# Reglages pour 'vim'
+# vim:set autoindent expandtab tabstop=4 shiftwidth=4:
+# cursor: 16 del