[tex]\bf \begin{cases}
f(x)=\sqrt{x+7}\\
g(x)=4x\\
h(x)=x^2\\
(f\circ g\circ h)(x)=f(~~g(~~h(x)~~)~~)
\end{cases}\\\\
-------------------------------\\\\
g(~~h(x)~~)=4\boxed{h(x)}\implies g(~~h(x)~~)=4\boxed{x^2}
\\\\\\
f(~~g(~~h(x)~~)~~)=\sqrt{\boxed{g(~~h(x)~~)}+7}
\\\\\\
f(~~g(~~h(x)~~)~~)=\sqrt{\boxed{4x^2}+7}[/tex]
