Question 128616
<pre>
If the length measures 3 inches more than the width, and the width is w, then
the length is w + 3.  We know that the perimeter of a rectangle is given by
{{{P[r]=2l + 2w}}}, so just substitute:


{{{P[r]=2(w+3)+2w}}} and we are given that {{{P[r]=78}}}


{{{2(w+3)+2w=78}}}


Distribute the 2 and remove the parentheses:
{{{2w+6+2w=78}}}


Collect like terms:
{{{4w+6=78}}}


Add -6 to both sides:
{{{4w=72}}}


And divide by 4:
{{{w=18}}}


The length is {{{w + 3=21}}}


Check:
2 times 21 is 42, 2 times 18 is 36, and 42 plus 36 is 78.  Answer checks.