Choose the ordered pair that is a solution to the system of equations -x plus y equals 12?

-x+y=12
is the equation of a line and since there are infinitely many points on the line and each point is represented by an ordered pair, we have infinitely many solutions.

If we take x as 0, then y must be 12
so (0,12) is one ordered pair that is a solution to the equation.
Zero is often a nice number to pick since it makes the calculation a bit easier.