[tex]f(zx)=-3x+5\to y=-3x+5\\\\\text{exchange x and y}\\\\x=-3y+5\\\\\text{solve for y}\\\\-3y+5=x\qquad\text{subtract 5 from both sides}\\\\-3y=x-5\qquad\text{divide both side by (-3)}\\\\y=-\dfrac{1}{3}x+\dfrac{5}{3}\\\\Answer:\ \boxed{f^{-1}(x)=-\dfrac{1}{3}x+\dfrac{5}{3}}[/tex]
