answer:
6 classes
reason:
to solve for x, make an equation
for members, the cost would be 6+3x
for nonmembers, the cost is simply 4x
this makes the equation to find when the cost is equal 6+3x=4x
subtract 3x from both sides to get 6=x
you can check by plugging 6 into x on both sides, which will give you $24 on each side, making it equal