Mike, Sam and James play football. Mike scores 8 more goals than James. Sam scores 5 more goals than Mike. Altogether they score 72 goals. How many did Sam score?

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.