Four times the sum of 4 and some number is 40

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

The perimeter of a rectangle is 42 inches. if the width of the rectangle is 6 inches, what is the length

Atransformation t : (x,y) (x-5,y +3) the image of a(2,-1) is