Find the Inverse Function Of $f$ $f ( x ) = 3 x + 6$

Multiple Choice

Find the inverse function of $f$ . $f ( x ) = 3 x + 6$

A) $f ^ { - 1 } ( x ) = \frac { ( x + 6 ) } { 3 }$
B) $f ^ { - 1 } ( x ) = \frac { ( x - 6 ) } { 3 }$
C) $f ^ { - 1 } ( x ) = \frac { 3 } { ( x - 6 ) }$
D) $f ^ { - 1 } ( x ) = \frac { 1 } { 3 } x - 6$
E) $f ^ { - 1 } ( x ) = \frac { 3 } { ( x + 6 ) }$