Answer:
Gym B would be the better option for going short term because you don't spend 100$. Now if you want to go more of long term id say Gym A, sure the 100 is a lot but lets look at a year basis.
Starting off Gym A is $120
Gym B is $30
12x20= 240 so for a whole year with gym A you spend 340
30x12= 360, so with a whole year in Gym B its 360.
you save $20 with gym A in a year.
Explanation: