The pie store is having a 20%, percent off sale on all of its pies. if the pie you want regularly costs $18 dollar how much would you save with the discount?

Could someone me with this question i’ve been stuck on it for 20 minutes

Arational number that is equivalent to -20/4?

Three students, javier, sam, and corrine, participated in a fundraiser where people donated a certain amount of money per lap that the student ran. each student also had some initial donations that were collected before the run. the equations that represent each student's total donation, y, based on the number of laps ran, x, is shown below. match each equation with the correct rate of change for that student.