Question 41228
20*12=240 sq in for framing 

(20-2x)(12-2x)=84 or 240-64x+4x~2=84 or 4x~2-64x+192 or x~2-16x+48=0 or

(x-12)(x-4) =0 or x=12 x=4 proof 12*4=48 sq in for the picture ASSUMING THE FRAME IS THE SAME THICKNESS ALL AROUND.