How did you get A => 9x+36=63 and 9x+54=81
A is first nine integars
x, x+1, ... , x+8 = 9x + (1+2+...+8) = 9x + 36
And in my opinion, we should not worry about calculating the answer. We should concentrate on finding if we can calculate it or not.
Two equations and two variables will give answer. I will leave the question the moment i have the equations.