The given function is f(x) = 3x/(x-4)

we have to find the inverse of this function;

first we have to calculate the value of x from the given function;

y = 3x / ( x - 4)

xy - 4y = 3x

xy - 3x = 4y

x( y -3 ) = 4y;

x = 4y / ( y - 3)

then,

y = 4x /(x - 3)

now f^-1(x) = 4x / (x - 3)