For the Given Functions F and G, Find the Requested $f ( x ) = 7 x + 6$

Multiple Choice

For the given functions f and g, find the requested function.
-If $f ( x ) = 7 x + 6$ and $g ( x ) = 3 x - 1$ , find (f $g ) ( x )$ .

A) $21 x - 1$
B) $21 x + 5$
C) $21 x + 13$
D) $21 \mathrm { x } + 17$