Chapter 2 - Section 2.7 - Absolute Value Inequalities - Exercise Set - Page 106: 87

$P(\text{rolling a }1\text{ or } 3)=\dfrac{1}{3}$

Of the total 6 sides of a die, 1 side has 1 dot and another 1 side has 3 dots. Hence the probability of rolling a $1$ or $3$ is \begin{array}{l}\require{cancel} P(\text{rolling a }1\text{ or } 3)=\dfrac{2}{6} \\\\ P(\text{rolling a }1\text{ or } 3)=\dfrac{1}{3} .\end{array}