Answer:
C) 6 ft
Step-by-step explanation:
Perimeter is just adding the side lengths together so...
31-15-10=x
6=x
so your answer is 6ft
if 3/5 are boys
1- 3/5
5/5 -3/5 = 2/5 are girls
2/5 * 30 = 60/5 = 12
12 are girls