Question 484692
<pre>
The other tutor did not prove it.  Here is the proof.

 (4*a+3)-3*a =

 (4*a+3) + (-3*a)   by the definition of subtraction

 4*a + [3 + (-3*a)] by the associative principle for addition 

 4*a + [(-3*a) + 3] by the commutative principle for addition 

 [4*a + (-3*a)] + 3 by the associative principle for addition

 {[4 + (-3)]*a} + 3  by the distributive principle of multiplication 
                             over addition

 1*a + 3            by the operation of addition 4+(-3) = 1

   a + 3            by the identity property for multiplication.

Edwin</pre>