Answer
a) $f(50)\approx 6.325$
b) $x= 59$
Work Step by Step
Given $$f(x)=\sqrt{x-10}.\tag{1}$$ a) Set $x= 50$ in equation $(1)$ and determine $f(50)$:
\begin{equation}
\begin{aligned}
f(50)&=\sqrt{50-10} \\
&=\sqrt{40}\\
&\approx 6.325.
\end{aligned}
\end{equation} b) Set $f(x)=7$ in equation $(1)$ and solve for $x$:
\begin{equation}
\begin{aligned}
f(x) & =7 \\
\sqrt{x-10}& =7 \\
\left(\sqrt{x-10}\right)^2& = \left(7\right)^2\\
x-10&=49\\
x&= 49+10\\
x&= 59.
\end{aligned}
\end{equation}
