Never mind the question. I want to try to solve that on my own. What I want to understand is how this: "Hint. $1 = ar + bs_1,\ 1 = ar + bs_2$" relates to solving it.
I'm a little confused by this statement, especially since it applies to integers.
If we say ar + bs = 1, that says to me that you have different multiples of r and s. And when you add those multiples you get 1. How can this happen unless you are adding fraction together or something, or one expression equals 1 while the other equals 0?