So you are setting the two expressions equal to each other.
buying a membership card and paying each time looks like this: 20 + 2x where x is the number of times you go to the gym. 20 dollars base then 2 each time you go.
4 each time you go is just 4x
so just set the two equal to each other.
20 + 2x = 4x
If you solve it you will get x = something, which would be the number of times to make the two equal.
