The original dimensions were W inches wide and (W + 6) inches long. After making the box, dimensions of its base are (W-2*3) wide and ((W+6)-2*3) long. The volume is 3*(W-6)*W, and the equation to find W is 3W*(W-6) = 336, or W^2 - 6W - 112 = 0. (W-14)*(W+8) = 0 W = 14. ANSWER. The original dimensions were 14 by 20 inches.