D is the answer to your question
Formula for perimeter a+b+a+b
12+5+12+5= 17+17= 34 .34=P
<em>x = 8</em>
Step-by-step explanation:

Add 1 to both sides.

Add 2x to both sides.

Divide 40 by 5.
x = 8
the lines are perpendicular because they're crossing each other