Answer:
Method 1:
[tex] \frac{1}{3} = - \frac{1}{3} x + 3[/tex]
[tex] - \frac{1}{3} x = - \frac{8}{3} [/tex]
[tex]x = 8[/tex]
Method 2:
[tex]f(x) = - \frac{1}{3} x + 3[/tex]
[tex] - \frac{1}{3} {f}^{ - 1} (x) = x - 3[/tex]
[tex] {f}^{ - 1} (x) = - 3x + 9[/tex]
[tex] {f}^{ - 1} ( \frac{1}{3} ) = - 3( \frac{1}{3} ) + 9 = - 1 + 9 = 8[/tex]
