PLEASE HELP! WILL MARK BRAINLIEST: How many terms of the arithmetic sequence -1, 2, 5,… must be added to get 609?

Afitness center has 2 membership plans one has a low dollar sign up fee of 15 dollars and costs 38 dollars per month to join. a second plan has a higher sign up fee of 78 dollars but a lower monthly fee of 31 dollars for what number of days of the month is the coat the same