2x+1/2y=7 correct value of x and y

If a baby uses 15 diapers in 2 days, how many diapers will the baby use in a year?

Asphere has a diameter of 10 in. what is the volume of the sphere?

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