Expression for the calculation triple 3 and add double 8

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?

How do i start to solve? would appreciate a walk-thru! a bird sitting 16ft above the ground in an apple tree dislodges an apple. after how many seconds does the apple land on the ground? (assuming that no branches will interfere with it's fall)

Which graph represents the equation y =4x