If anyone can help me please with the this problem (picture above)

Answer:
6x-3=9
Step-by-step explanation:
i dont really get what it means by set up an equation but heres what i know-
36 is the perimeter so divide it by 4 to get the length of each side-
36/4=9
now you know that each side is 9, so 6x-3=9
when you solve that, x=2