Answer :
If it costs her [ 37x + 20 ] to be a member of the gym for 'x' months,
that means that it cost her 20 at the beginning just to sign up, before
any time went by, and then another 37 every month after that.
that means that it cost her 20 at the beginning just to sign up, before
any time went by, and then another 37 every month after that.