How do you find the permiter of a square? anyone ! !

In the polynomial below, what number should replace the question mark to produce a difference of squares? x2 + ? x - 36

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.

Find the value of x. round the length to the nearest tenth