What is 3+3-3= you anwers it for some points

Which is an equation for the nth terms of the sequence 12,15,18,21

Josh has a rewards card for a movie theater he receives 15 points for becoming a rewards card holder he earns 3.5 points for each visit to the movie theater he needs at least 55 points to earn a free movie ticket which inequality can josh use to determine x, the minimum number of visits he needs to earn his first free movie ticket.

Write the expression 7x^3-28xy^2 as the product of 3 factors