At what position on the number line is the red dot located?

The square root of 9x plus 7 plus the square rot of 2x equall to 7

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

Will give a: 122 b: 90 c: 48 d: 180