Question 7664
Perimeter of rectangle, P = 2(L + W)

In your problem, P = (6x+6) and W = x, so you can write:

{{{(6x+6) = 2(L+x)}}} Solve this for L:

{{{6x + 6 = 2L + 2x}}} Subtract 2x from both sides.

{{{4x + 6 = 2L}}} Divide both sides by 2.

{{{L = 2x + 3}}}

Check:

{{{P = 2(L+W)}}}
{{{P = 2((2x+3)+x)}}}
{{{P = 2(3x+3)}}}
{{{P = 6x + 6}}}