The points (-9,-10) and (n,-9) fall on a line with a slope of 1 . what is the value of n

Can any one me with the answers to these questions asap?

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.

2.5 milligrams is equivalent to how many grams