What is a constant?
A constant is something that doesn't change overtime; a steady flow that has a fixed value in a given situation.
First, we would need to see how much the gym charges each month for a membership, based on the amount he pays every year.
If we know that a year has 12 months, and every year he pays $252, we can use an equation that looks like this:
252 ÷ 12 = 21
The gym charges $21 every month for a membership.
Given, if m = months, and c = total amount he paid, the equation would look like this:
21 × m = c
Therefore, an equation you can use to figure out how much he pays in (m) months is 21 × m = c.