Question 872809
The frame width is needed and should be found first.  Let x be this width.


{{{(17+2x)(11+2x)}}}=Area inside the outer dimensions of the frame plus picture.
{{{(2x+17)(2x+11)=315}}}, total area of painting plus frame.
{{{4x^2+34x+22x+17*11=315}}}
{{{4x^2+56x=128}}}
{{{highlight_green(x^2+14x-32=0)}}}
{{{(x-2)(x+16)=0}}}
-
The realistic value for x is 2.
{{{highlight(x=2)}}}
-
Dimensions of the frame on the outside are 21 and 15 inches.