If (1/4)^x+y=256 and log(small4)(x-y)=3, calculate the exact values of x and y algebraically. Please help me out. Thank you!

since 1/4 = 4^-1 and 256 = 4^4 = 1/4^-4, you have

1/4^(x+y) = 1/4^-4
log_4(x-y) = 3 means x-y = 4^3
so now just solve
x+y = -4
x-y = 64
now solve for x and y