Question 1015137
at least 2 bottles:
find probability of 0, 1.  You don't want that, but if you subtract that value from 1, you will get what you do want.
probability of 0 is 0.85^10, because that means all are not defective.
p(0)=0.1969
p(1)=10 ways it can happen*(0.85^9)(0.15)^1
=0.3474
The sum of p(0) and p(1)=0.5443
At least 2 bottles are defective is 1-0.5443 or 0.4557.
This is easier than computing the nine probabilities from p(2) to p(10), although the last few will be essentially 0.