Mary and tom were buying a present for their mother on mothers day. mary spent $12 and tom spent $28 if they wanted to share the cost equally, how much money does mary owe tom?

16 dollars is how much mary owes tom

12 + 28 = 40 ... so they spent $40. To make it even, they would have to spend (40/2) = 20 bucks a piece.

Tom spent 28 ... Mary spent 12 ... if Tom lends Mary 8 bucks, they will have both spent 20. So Mary owes Tom 8 bucks