It is a solution to the system. The best way to tell this is to try the ordered pair in each of the equations.
2x - 3y = -21
2(-3) - 3(5) = -21
-6 - 15 = -21
-21 = -21 (TRUE)
3x - y = -14
3(-3) - (5) = -14
- 9 - 5 = -14
-14 = -14 (TRUE)
Since both equations come out true, it must be a solution.
