For every 8 chin-ups Doug did during the physical fitness test, Adam did 3. Doug was able to do 15 more chin-ups than Adam. How may chin-ups did Adam do?

Answer 1

number of push-ups for Doug = 8x
number of push-ups for Adam = 3x

solve:

8x - 3x = 15

take over

Answer 2

8x - 3x = 15
//Combine like terms
5x = 15
//Divide both sides by 5 to get x on one side
5x / 5 = 15 / 5
x = 3

//Test
8(3) - 3(3) = 15
24 - 9 = 15