At a local fitness center, members pay an $8 membership fee and $4 for each aerobic class. Nonmembers pay $6 for each aerobic class. For what number of aerobics classes will the cost for members and nonmember be the same?

An aerobic lesson will be defined as 'a'

For every member lesson, they pay $4, so they will be represented as 4a

For every non member lesson, they pay $6, so they are 6a

Don't forget members have to pay $8 at the start, so they have to be 4a + 8

So

4a + 8 = 6a is our final equation

Move the 'a's to one side, by subtracting 4a from each side, giving you

8 = 2a

Divide by 2 to isolate a

4 = a

After 4 aerobics classes, the cost will be the same

After 4 classes the cost would be the same ($24)