Answer: So for x, when you go to the next box on the bottom of 21, you subtract 7 from 21. Then you subtract 7 from the one you did before so it will be 14 minus 7.
Then for y, you add 1. So you add 1 to 7 and you have that answer. When you have your answer, which is eight, you add 1. So, 8 plus 1 and then you have your answer.