-3 = 7 - BLANK pls tell me what blank is

The figure above shows the lengths of thesides of a rectangle in cm. find the valuesof x and y and then the area of the rectangle. sides: top= 3x - yleft= 3y + 4bottom= 2x + yright= 2x - 3 use both methods, elimination and substitution, if possible.

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

What is 140% of 25? because i need