This is the answer.
Copy machine "A" has a 10% chance of breaking down. Machine "B" has a 7% chance of breaking down. If 1 machine broke down, what are the odds that it will be machine "B".
My neighbor has this question in her book. The answer is given in the back of the book to be 70/163 - but we are not able to figure out how they came to this answer. Any help would be appreciated.