If she has 6 dogs and can only walk 2 at a time, she can take 3 pairs of dogs out.
85% liked => 15% didn't like
30 = 15% of x
30 = 0.15 x => x = 30 / 0.15 = 200. This is the total number of students at the library.
Then 200 - 30 = 170 is the number of students whom did like reading mistery stories.
Answer: 170.
You made the choice to choose the letter A, a second time.