PLEASE HELP ME I AM BEHIND A LOT!!!!!

Hi There!
Step-by-step explanation:
Perimeter = 37 meters
Side 1 = 18 meters
Side 2 = 11 meters
Side 3 = ?
To solve the 3rd side just add both other sides then subtract by the perimeter:
18 + 11 = 29
37 - 29 = 8
Answer:
Side 3 is equal to 8 meters.
Hope This Helps :)