Charlie made 221 for 13 hour of work. at the same rate, how many hours would he have to work to make 289?

You have 17 cats that live in houses on your street, 24 dogs, 3 fish, and 4 hamsters. what percent of animals on your block are dogs?

Apinhole camera is made out of a light-tight box with a piece of film attached to one side and pinhole on the opposite side. the optimum diameter d(in millimeters) of the pinhole can be modeled by d=1.9[ (5.5 x 10^-4) l) ] ^1/2, where l is the length of the camera box (in millimeters). what is the optimum diameter for a pinhole camera if the camera box has a length of 10 centimeters

3x + 4y = 5 x- 3y = -7 solve by substitution