Projected Picture

The area of a projected picture on a movie screen varies directly as the square of the distance from the projector to the screen. If a distance of 20 feet produces a picture with an area of 6[c]square feet, what distance produces an area of 1[a]0 square feet? Round to the nearest tenth of a foot.

Note: if[a]=2, then 1[a]0=120 feet, and if[c]=8, then 6[c]=68 feet

a=3,c=8,