I need some help with this, it doesn't make much sense to me.

Ineed to know the rule for the sequence. plz !

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

In the sixth grade 13 out of 20 students have a dog if there are 152 sixth grade students how many of them have a dog