Answer
$f=4\pi$
Work Step by Step
Use the Subtraction Property of Equality by subtracting $3\pi$ from each side of the equation:
$$\begin{align*}
f+3\pi-3\pi&=7\pi-3\pi\\
f&=4\pi\end{align*}$$
Check the solution by substituting $4\pi$ to the variable in the given equation:
$$\begin{align*}
f+3\pi&=7\pi\\
4\pi+3\pi&\stackrel{?}{=}7\pi\\
7\pi&\stackrel{\checkmark}{=}7\pi\end{align*}$$
Thus, the solution is $f=4\pi$.
