I'm not sure about the given data but I plotted the scatter plot based on what I understand on how the data should be presented.
Time (years)
3, 6, 9, 12, 15, 18, 21, 24
Number of participants(x1000)
22, 25, 28, 14, 17, 20,15, 9
Attached is the scatter plot created online.
x = time (years)
y = number of participants
Just take 1 divided by 6
1/6=0.16666667
The answer is B that's the answer
Calculating the other leg:
other leg^2 = 13^2 - 5^2
other leg^2 = 169 -25
other leg^2 = 144
other leg = 12
Area = .5 * 12 *5
Area = 30 sq feet
answer is A