Answer:
You are correct if rounding to the nearest whole number.
I got 12.69 so if you round up, you will get 13 (see below)
Explanation:
X*Y = 288
(X-a)*(Y-a) = 10 * 8 = 80
X-a = 10
Y-a = 8
a = Y-8 = X-10
(X-10) * X = 288
X^2 - 10X = 288
X^2-10X-288= 0
quadratic equation
X = (10 + 35.38)/2 =22.69 (technically it would have 2 answers, but we only want to evaluate the positive answer)
a = X- 10 = 22.69- 10 = 12.69 which would round up to 13 if you are rounding to the nearest whole number.
HOPE THIS HELPS!!!