the answer is a. the first step is to divide the whole bottom equation by -1 because x can’t be negative. you then plug in y + 9 into the first equation to solve. so the equation would be (y + 9) + y = 11. you do this because in substitution you plug in one of the equations into the other equation. you then get 2y + 9= 11. you would next subtract 9 to both sides which leaves you with 2y= 2, divide by both sides, y = 1. you then plug the why value into the first equation to figure out the value for x. so it would be x + 1 = 11, subtract 1, x equals 10.
sorry this was hard to explain! hope this helps!