DO NOT SEND LINKS OR ANYTHING LIKE THAT Given the equation y=-3x+2.5
When y is 8.5, what of x makes the equation true?

PLEASE, PLEASE, PLEASE, HELP

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