Nick was thinking of a number. Nick doubles it, then adds 15 to get an answer of 77.4. What was the original number?

Barrett is comparing the membership fees for two museums.the art museum charges a one-time fee of $8.25 plus $2.25 per month. the science museum charges a one-time fee of $10.75 plus $3.50 per month. how much does barrett save by joining the art museum instead of the science museum?