Question

your cell phone carrier charges $0.18 for each extra minute over your limit.if the total shows that you owe $3.24 for extra minutes, how many minutes did you go over

Answer 1

If you have
$\dfrac{1 \ min}{0.18 \ dollars}$
as your cost,
and you paid
$3.24 \ dollars$,
then 
$(\dfrac{1 \ min}{0.18 \ dollars})(3.24 \ dollars)=18 \ min$.

Thankfully, most cellphone companies don't charge for minutes anymore!