Please Evaluate this expression...4a-2b for a-5 and b=3

Combine like terms to make a simpler expression 3z+z

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

How to write four times a number,minus 6,is equal to theee times the number+8 as an equqtion