Find the twenty-seventh term of the arithmetic sequence 21, 18, 15, ...

Based on what i know about mean, this doesn't add up.

What is the product? a-3/15a × 5/a-3

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