Which graph represents a nonlinear function?

How do i do this activity, is appreciated

The tuition costs, c, for a local community college are modeled by c(h) = 250 + 200h, where h represents the number of credit hours taken. the local state university has tuition costs, s, modeled by the function s(h) = 300 + 180h. how many credit hours will a student have to take for the two tuition costs to be equal? round the answer to the nearest tenth of an hour.

For the following geometric sequence, find the recursive formula. {-80, 20, -5, } i need : ')