Answer
$80$ minutes.
Work Step by Step
Let the minutes of local calls is $x$.
Monthly charge $=9.95+.035x$.
Last month paid $=\$12.75$.
The mathematical equation is
$\Rightarrow 9.95+.035x=12.75$
Subtract $9.95$ from both sides.
$\Rightarrow 9.95+.035x-9.95=12.75-9.95$
Simplify.
$\Rightarrow .035x=2.8$
Divide both sides by $.035$.
$\Rightarrow \frac{.035x}{.035}=\frac{2.8}{.035}$
Simplify.
$\Rightarrow x=80$
Hence, the number of minutes of local calls is $80$ minutes.
