A vendor has $9$ different fruits. In how many ways can he select $3$ fruits?

The number of ways to select $r$ items out of $n$ items is given by the combination formula $\left(\genfrac{}{}{0ex}{}{n}{r}\right)$:
$$\text{Number of ways}=\left(\genfrac{}{}{0ex}{}{9}{3}\right)=\frac{9\times 8\times 7}{3\times 2\times 1}$$

$$\text{Number of ways}=3\times 4\times 7=84$$