What's a situation that can be represented by the opposite of -42

Ateacher has $80 to buy workbooks. each work book cost $3. if she buys as many workbooks as possible, how much money does she have leftover? a) $2 b) $4 c) $6 d) $8

Pls! does anybody know a shortcut for answering these types of questions in the future?

The amount spent on food and drink by 20 customers is shown below what is the modal amount spent and the median amount spent? 40 25 8 36 18 15 24 27 43 9 12 19 22 34 31 20 26 19 17 28