Because the rectangle has four sides double both your 2x and your 3.25x +1
your equation should look like this
2x+2x+3.25x+1+3.25x+1=65
(65 is your perimeter)
combine like terms
10.5x+2=65
subtract 2 from both sides
10.5x=63
Divide both sides by your x (10.5) you are left with
x=6 thus getting your answer