Here you have 2 linear equations and are to solve this system. Both equations have already been solved for y, so you can set one of them = to the other one:
-2x+11 = -3x+21.
Then 3x-2x = 21 - 11, or x = 10 (answer)
Find y by subst. x = 10 into either of the given equations.
Solution is then (10, ? )
