Given a triangle with perimeter 63 cm, one side of which is 21 cm, and one of the medians is perpendicular to one of its angle bisectors. Find the lengths of all sides of the triangle.

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.