Consider,

. Let's say

then the problem reduces to

. (Do you understand this step?)
So then replacing a again with our definition we get,

.
(5*7) - (5*4) = 35 - 20 = 15
you "distribute" the 5 but multiplying it to both numbers in the parentheses, and doing the subtraction.
The process of moving a figure to a different location is called TRANSFORMATION.