For those who don't know, Pi is defined as the ratio of a circle's circumference to its diameter. The first 15 digits of the never-ending number are: 3.14159265358979.Mar 14, 2013
Answer:
0.0975 or 9.75%
Step-by-step explanation:
Assuming that no engines fail simultaneously, the probability that exactly one engine fails is the probability that the first engine fails (15%) multiplied by the probability that the second engine does not fail (100% - 35%):

The probability of exactly one engine failure is 0.0975 or 9.75%
EDIT:
Order of operations doesn't matter in addition. So you can add them in any order.