Question 445637
Let x in be the thickness of the frame.
...
So,
12-2x will be the width of the picture after you take out the frame.
and 19-2x will be the length of the picture.
...
l*w=A
{{{(19-2x)(12-2x)=78}}}
*[invoke explain_simplification "(19-2x)(12-2x)" ]
{{{4*x^2-62*x+228=78}}}
{{{4*x^2-62*x+228-78=0}}}
{{{4*x^2-62*x+150=0}}}
*[invoke quadratic "x", 4, -62, 150 ]
So therefore there are two answers 12.5 and 3.
But, this is dealing with length and area so the answer can't be a negative number.  The equation was (19-2x)(12-2x)  If the answer was 6 or more then the (12-2x) would make it negative or 0.  So therefore, the answer is 3.
The thickness of the frame is 3 in.