Let James = x
Mike = x+8
Sam = Mike+5 = (x+8)+5 = x+13
Altogether: James + Mike + Sam = 72
Therefore, x + (x+8) + (x+13) = 72
Now solve for x: 3x + 21 = 72
Bring 21 to the other side: 3x = 72-21 = 51
Divide by 3 on both sides: x = 17
Going back to the beginning: Sam = x +13, therefore Sam = 17+13 = 30
Sam scored 30 goals.