Question 129299
If the thickness of the frame is x, and there are two thicknesses in each dimension, and the outer dimensions are 15 X 13, then the inside .dimensions must be 15 - 2x and 13 - 2x, and these also happend to be the dimensions of the picture that is showing.


So, since the area of the picture that is showing is 156, we can say:


{{{(15-2x)(13-2x)=156}}}


All you have to do is multiply this out and solve the resulting quadratic.  If you need help with that, write back.