Answer
$y=f[g(x)],$
$f(x)=x^{2/3},\qquad g(x)=3x^{2}-7$
Work Step by Step
A reliable method is asking:
"How would we calculate this on a calculator?".
First, calculate $g(x)=3x^{2}-7$
and then, calculate: $\quad [$the result, g(x) $]^{2/3}$
(apply $f(x)=x^{2/3}$ on g(x) instead of x)
$f[g(x)]=[g(x)]^{2/3}=(3x^{2}-7)^{2/3}=y$