First you add 3 twice to both sides of the swimming pool
12 + 6 = 18
15 + 6 = 21
The perimeter is the sum of all sides therefore
18 + 18 + 21 + 21 = 78
The answer is A
Answer:

Step-by-step explanation:
I used an online Fraction calculator to check my answer and I got 4/15 both times so you can trust this answer my friend.
Hope this helped you out.