Verify that the function f(x)=1/20x + 1/20 with the domain {2,5,10} is a valid p. d.f of a discrete random variable X

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.

Which will form a composite function?

Walking at a constant rate of 8 kilometers per hour, juan can cross a bridge in 6 minutes. what is the length of the bridge in meters?