The percent change of 15 yards to 18 yards

First we subtract it:

18 - 15 = 3

Now we divide it to the original:

3 / 15 = 0.2

Multiply by 100:

0.2 * 100 = 20%

You need to include the original coordinates of the triangle to answer this. and how much does it translate (move left right up down)

It's like discovering the answer to a puzzle. the purpose in solving an equation is to find the value or values of the variable that makes it a true statement. any value of the variable that makes the equation true is called a solution to the equation.