A triangle has a perimeter of 23 feet. Find the value of X

The sum of two numbers is 12 and their difference is 18 what are the two numbers

If a || b and e || f , what if the value of y ?

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