Answer:
11/2, 22/4, 33/6, 44/8, 55/10, 66/12, 77/14, 88/16, 99/18, 110/20, 121/22, 132/24, 143/26, 154/28, 165/30, 176/32, 187/34, 198/36, 209/38, 220/40, and so on ...
Suzie needs enough trim to cover the perimeter of the triangle. So she need enough to cover each side of 18. Thus 18 x 3 = 54 and 54 is your answer.
You’re answer would be x=18.28