Question 252367
Given,    4^x / 2^x+y = 8
          2^2x /2^x+y = 2^3
          2^(2x-x-y)  = 2^3
          2^(x-y)     = 2^3
Therefore,       x-y  = 3   ...(1)

Next,    9^(x+y) / 3^5y = 243
         3^2(x+y)/3^5y  = 3^5
         3^(2x+2y-5y)   = 3^5
         3^(2x-3y)      = 3^5
Therefore,       2x-3y  = 5   ...(2)
Solving (1) and (2),
2x(1)-(2):
          (2x-2y)-(2x-3y) = 6-5
                        y = 1