Can anyone answer and explain??

Rai compares two cable plans from different companies. which equation gives the correct value of mm, the number of months for which plans a and b cost the same?

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

F(x)=5/6x+3 which of the following is true