well, (f o g)(4) is just another way of saying f( g(4) ).
so, we can simply first find g(4), and then plug that in f(x),
[tex]\bf \begin{cases}
f(x)&=3x+1\\
g(x)&=x^2-6\\
(f\circ g)(4)&=f(~~g(4)~~)
\end{cases}
\\\\\\
g(4)=(4)^2-6\implies g(4)=16-6\implies g(4)=10
\\\\\\
f(~~g(4)~~)\implies f(~~10~~)=3(10)+1\implies f(~~10~~)=31[/tex]
