Answer
See below.
Work Step by Step
If two events $A,B$ are not mutually exclusive, then $P(\text{A or B})=P(A)+P(B)-P(\text{A and B})$ and $P( \text{A and B}))\ne0$.
Assume we have the integers from $1$ to $10$ and we want to find the probability of randomly choosing a number less than $3$ or being odd. Then here the probability $P( \text{A and B})=P( \text{less than 3 and odd})=P( \text{selecting the number 1})=\frac{1}{10}$. Then the probability for this: $\frac{2}{10}+\frac{5}{10}-\frac{1}{10}=\frac{6}{10}$
