Question 7856
Perimeter of a rectangle is: P = 2(L + W)

Here: L = 2x+6 and W = 2x.  Substitute these into the above formula.

{{{P = 2(2x+6 + 2x)}}}
{{{P = 2(4x + 6)}}}
{{{P = 8x + 12}}} and this is as far as you can go until you know the value of x.