If you have
[tex] \dfrac{1 \ min}{0.18 \ dollars} [/tex]
as your cost,
and you paid
[tex]3.24 \ dollars[/tex],
then
[tex](\dfrac{1 \ min}{0.18 \ dollars})(3.24 \ dollars)=18 \ min[/tex].
Thankfully, most cellphone companies don't charge for minutes anymore!
