Given that the width of the rectangular piccture is:
[tex]w=\frac{1}{2}l[/tex]Where "l" is the length of the picture.
You know that the perimeter is:
[tex]P=72\text{ }in[/tex]The formula for calculating the perimeter of a rectangle is:
[tex]P=2l+2w[/tex]Where "l" is the length and "w" is the width.
Therefore, you can substitute the perimeter and the width into the formula, in order to find "l":
[tex]72=2l+2(\frac{1}{2}l)[/tex]Now you can solve for "l":
[tex]72=2l+\frac{2}{2}l[/tex][tex]72=2l+l[/tex][tex]72=3l[/tex][tex]\frac{72}{3}=l[/tex][tex]l=24\text{ }in[/tex]Hence, the answer is:
[tex]l=24\text{ }in[/tex]