diff --git a/python_symb/tools.py b/python_symb/IndependantTools/tools.py
similarity index 52%
rename from python_symb/tools.py
rename to python_symb/IndependantTools/tools.py
index 3d3b00a..b200348 100644
--- a/python_symb/tools.py
+++ b/python_symb/IndependantTools/tools.py
@@ -3,6 +3,12 @@ from typing import *
 
 
 def gcd(a, b):
+    """
+    Greatest common divisor
+    work with any object that support modulo and comparison (contrary to math.gcd)
+
+    used in type : Fraction
+    """
 
     if b > a:
         return gcd(b, a)
diff --git a/python_symb/symbols.py b/python_symb/MathTypes/symbols.py
similarity index 53%
rename from python_symb/symbols.py
rename to python_symb/MathTypes/symbols.py
index 1922db7..00c620a 100644
--- a/python_symb/symbols.py
+++ b/python_symb/MathTypes/symbols.py
@@ -1,5 +1,5 @@
 from __future__ import annotations
-# from expr import Expr
+
 
 
 class Symbols:
@@ -18,6 +18,22 @@ class Symbols:
     def __str__(self):
         return self.name
 
+    def __add__(self, other):
+        from python_symb.Expressions.expr import Expr
+        return Expr('+', [self, other])
+
+    def __radd__(self, other):
+        from python_symb.Expressions.expr import Expr
+        return Expr('+', [other, self])
+
+    def __mul__(self, other):
+        from python_symb.Expressions.expr import Expr
+        return Expr('*', [self, other])
+
+    def __rmul__(self, other):
+        from python_symb.Expressions.expr import Expr
+        return Expr('*', [other, self])
+
 
 class Var(Symbols):
     """
@@ -29,6 +45,4 @@ class Var(Symbols):
         super().__init__(name)
         self.__class__.instances.append(self)
 
-    """def __add__(self, other) -> Expr:
-        return Expr('+', [self, other])"""