How does x squared minus y squared equal 901?

It can. You can make it happen. The problem is that you may not be able to get whole number answers

Here's the general equation.

x^2 - y^2 = 901 Suppose you make y = 15. what will x be?

x^2 - 15^2 = 901

x^2 - 225 = 901 Add 225 to both sides.

x^2 = 1126 Now take the square root of 1125

sqrt (x^2) = sqrt (1126)

x = + / - 33.556

That's one example. Just pick others and use your square root button. I don't think there's a whole number answer, but I could be wrong.