find the inverse of

f(x)=-5+log(base5)(y-5)

y = 5 + log_5(x-5)

y-5 = log_5(x-5)
5^(y-5) = x-5
x = 5 + 5^(y-5)

so, f^-1(x) = 5 + 5^(x-5)