Help idk how to do pls help

Find the missing factor. 7s2 + 25s + 12 = (s + 3)( ).

Use the elimination method to solve the systems of equations.choose the correct ordered pair. 7x+4y=39

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