You plug the equation that equals y into the y value on the other equation that equals 4. Then, you plug the x value into the x on the equation that equals y. Sorry if that was confusing
First we combine the parenthesis to get 9/(-2-i) then we multiply both the numerator and the denomenator by the conjugate of -2-i (whic is -2+i) to get (-18+9i)/5