Simultaneous equation

x = 5, y = 9.

Step-by-step explanation:

8^x / 2^y = 64

3^4x * (1/9)^(y -1) = 81

From the first equation

2^3x / 2^y = 2^6

2^(3x-y) = 2^6

So 3x - y = 6  (1)

From the second equation:

3^4x * 9^(-(y-1)) =  3^4

3^4x * 3^2(-(y-1)) = 3^4

3^(4x+ 2(1 - y)) = 3^4

So 4x + 2(1 - y) = 4

4x - 2y = 2

2x - y = 1   (2)

Subtract: (1) - (2):

x = 5.

and  2(5) - y = 1

so y = 9.