Answer: The probability that a randomly selected tire will have a tread-life of less than 65,000 miles is 0.7872 .
Step-by-step explanation:
The cumulative distribution function for exponential distribution is :-
, where
is the mean of the distribution.
As per given , we have
Average tread-life of a certain brand of tire : 
Now , the probability that a randomly selected tire will have a tread-life of less than 65,000 miles will be :

Hence , the probability that a randomly selected tire will have a tread-life of less than 65,000 miles is 0.7872 .
I am not going to give you the answer, but I am going to tell you how to do it. You first put 18 over 1, and multiply that by one half. (You multiply across.)
9+10=?
9 = 3x3
10= 5x2
3 (from 3x3) x 5 (from 5x2) = 15
3 (from 3x3) x 2 (from 5x2) = 6
15+6=21
Therefore 9+10=21
The answer is A 3/10 because there is 3 blue marbles and all together there is 10