Given an interest of 11,900 at 6% for 50 days (ordinary interest) calculate the principal

Need this asap if anyone can i would be very grateful. if you could show workings that would really

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

Solve the equation. 2x - 8(x+1)= 6(2x - 3)