inverse

F(x) =  (2x)  / (x - 8)           

Write as

y =  (2x) / (x - 8)       multiply both sides by x - 8

y(x - 8)  = 2x       expand the left side

yx - 8y  = 2x

yx - 2x  =  8y

x(y - 2)  =  8y

x = 8y / (y - 2)       switch x and y

y = 8x / ( x - 2)       and we can write

F^-1(x)  = 8x / (x - 2)  .........      Note that x cannot  =  2