What minus what equals ninety and what plus what equals six hundred thirty?

Answer 1

There are an infinite number of answers to each question. So when you add the lists
of answers together, there are an infinite number of answers to both of them.

Here's one answer for each. When you take these two answers away from the
infinite number of answers, then there are only an infinite number more remaining.
91 - 1 = 90
629 + 1 = 630