Plz show ur work and plz plz plz tell me by september 15 2016

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?

Translate the word phrase into a math expression. 15 fewer than the product of 4 and a number. (pls immediately)

In a class, there are 12 girls. if the ratio of boys to girls is 5: 4 how many boys are there in the class