Kevin needs 2 yards to get back to original place.
picture a number line. the starting point is 0. go forward 5 which brings u to 5 on the number line. then since he lost 7 go back 7 which brings u to -2. now to get back to 0 you need to go forward 2. which means that he must gain 2 in order to get back to the starting point.
Kevin currently stands at -2 yards after gaining 5 yards and losing 7 yards. To return to the starting point of 0 yards, he needs to gain 2 yards on his next play.
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