Answer
$f\circ g\circ h=\sqrt{x-1}-1$
Work Step by Step
$f(x)=x-1$ $,$ $g(x)=\sqrt{x}$ $,$ $h(x)=x-1$
First, find $g\circ h$ by substituting $x$ by $h(x)$ in $g(x)$ and simplifying if possible. Then, substitute this function into $f(x)$ to find $f\circ g\circ h$:
$g\circ h=g(h(x))=\sqrt{x-1}$
$f\circ g\circ h=f(g(h(x)))=\sqrt{x-1}-1$