Can someone help me Solve for x

Atriangle with all sides of equal length is a/an triangle. a. right b. scalene c. equilateral d. isosceles

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

Which diagram shows lines that must be parallel lines cut by transversal?