Swap x and y, then solve for y.
y = 8x + 16 . . . . . . original function
x = 8y + 16 . . . . . . x and y swapped
x - 16 = 8y . . . . . . subtract 16
(x - 16)/8 = y . . . . .divide by 8. This is your inverse function.
[tex]f^{-1}(x)=\dfrac{x-16}{8}[/tex]
