Find the Composition $f ( x ) = \frac { 3 } { x + 5 }$

Multiple Choice

Find the composition.
-If $f ( x ) = \frac { 3 } { x + 5 }$ and $g ( x ) = \frac { 1 } { 7 x }$ , find $f [ g ( x ) ]$

A) $\frac { 1 x + 5 } { 21 x }$
B) $\frac { 21 x } { 1 + 35 x }$
C) $\frac { 3 x } { 1 + 35 x }$
D) $\frac { 21 x } { 1 - 35 x }$