Can someone please give me a good explanation of how to work this out! 15 points for a good answer.

6x - 8 = 16 solve the following equation. then place the correct number in the box provided.

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

Tommy buys a sweater that is on sale for 40% off the original price. the expression p -0.4p can be used to find the sale price of the sweater, where p is the original price of the sweater. if the original price of the sweater is 50, what is the sale price?