Question 118465
We know the perimeter of a rectangle is {{{P[r]=2l + 2w}}}.


In this case, {{{w = x}}}, so we can say that our perimeter is {{{2l+2x}}} by direct substitution.


We are also given that the perimeter is 6x + 6, so we can create the following equation:


{{{2l+2x=6x+6}}}.


Now solve for l:


{{{2l = 4x+6}}}
{{{l=2x+3}}}


Check:

{{{P[r]=2l+2w=2(2x+3)+2x=4x+6+2x=6x+6}}}