Answer
$21$ inches
Work Step by Step
Recall:
The perimeter $P$ of a rectangle is given by the formula $P=2(l+w)$where $w$=width and $l$=length.
The given rectangle has $w=3.5$ inches and $l=7$ inches.
Thus, its perimeter is:
\begin{align*}
P&=2(7+3.5) &\text{inches}\\
P&=2(10.5) &\text{inches}\\
P&=21 &\text{inches}
\end{align*}
