Answer
With $g(x)=x+3$, and $f(x)=\displaystyle \frac{1}{x}$,
$G(x)=f[g(x)]=f\circ g(x)$
Work Step by Step
If we were to calculate by hand,
we would first add 3 to the number$\qquad$...$ g(x)=x+3$,
then find its reciprocal $\qquad$ .... $f(x)=\displaystyle \frac{1}{x}$
In this way, $G(x)=f(g(x))=f\circ g(x)$