Question 303297
Let y = f(x)

y = 3x - 1

Switch y with x.

x = 3y - 1

Add 1 to both sides.

x + 1 = 3y

Divide both sides by 3.

(x + 1)/3 = y

Replace y with f^-1(x).

(x + 1)/3 = f^-1(x)