Please help find area

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

Acircus act has 3 times as many elephants as acrobats. jorge noticed that all together there were 56 legs in the circus ring. how many elephants were in the show?

George writes the mixed number as sum and uses the distributive property 1/2.-2/5=1/2-2+2/5=1/2