Answer: The probability that Travis will choose a mystery book is 1/3.
Explanation: To find the probability that Travis will choose a mystery book, we need to determine the ratio of the number of mystery books to the total number of books on Travis's shelf.
Travis has 6 mystery books, and the total number of books on his shelf is 6 + 5 + 4 + 3 = 18.
Therefore, the probability (in fraction form) that Travis will choose a mystery book is 6/18.
To simplify this fraction, we can divide both the numerator and denominator by their greatest common divisor, which is 6.
6 ÷ 6 = 1
18 ÷ 6 = 3
So, the simplified fraction is 1/3.