Can someone please help me

Cam bought some used books for $4.95. he paid $0.50 each for some books and $0.35 each for the others. he bought fewer than 8 books at each price. how many books did cam buy?

Julius sold five times as many computers as sam sold last year. in total, they sold 78 computers. how many computers did julius sell?

240 seventh graders and two-thirds of the students participate in after-school activities how many students participate in after-school activities