Answer:
0.85
Step-by-step explanation:
Given two events A and B, the probability that either A or B occurs is given by:
where
the probability that A occurs
is the probability that B occurs
is the probability that both A and B occur at the same time
In this problem, we know the following facts:
is the probability that the car requires an oil change
is the probability that the car requires a brake repair
is the probability that the car requires both an oil change and brake repair
Therefore, the probability that either o (car requiring oil change) or b (car requiring brake repait) occur is:
The plot of the PDF shows the distribution is symmetric. This means that the mean is the same as the median, and that the 50% of the distribution lies to other side of this mean, i.e.
For this distribution, 
.
There are 10 crosses, which means that there are 10 trees in total. If we distribute 5 gallons among 10 trees, we give each tree
5/10=1/2=0.5 gallons
I think choice a would be the correct answer. 90.
