So when one goes up, the other goes down. This is an inverse equation.
An inverse equation looks like this: y = 1/x
In this case, when parking fee (f) decreases, cars (c) increase.
You know which side to put each variable on using the chart they gave you.
f | c
20.00 15 (20.00 = x/15) x=300
30.00 10 (30.00 = x/10) x=300
So your equation in this case is f = 300/c
Knowing that, plug in the fee of 6.00
6 = 300/c Multiply both sides by c.
6c = 300 Divide both sides by 6.
c = 50 cars
