B I think but i could be totally wrong
The '68-95-99.7' rule says
-About 68% of values fall within one standard deviation of the mean.
-About 95% of the values fall within two standard deviations from the mean.
-Almost all of the values — about 99.7% — fall within three standard deviations from the mean.
Here 
Therefore, the probability

The required probability

P=2(L+W)
if length=7
and P=24
24=2(7+W)
divide both sdes by 2
12=7+W
minus 7both sides
5=W
width=5meters
Answer:
A. 3
Step-by-step explanation:

REMEMBER to MULTIPLY FIRST!!
21 / 7 = 3