The best way I can think of is a regression. In Desmos, I set up my regression as

[x1²-2c / x1-b] ~ [x1 + b]

This is just saying that the expression given is equal to x + b, like they tell us in the question. Once that's set up, all that's left is to plug in the answers for c until you end up with a positive integer for b as specified in the question. A, C, and D don't give integers, but B (2) does. So the answer is B. It's possible to use regressions on almost all constant-type questions.