Choose a number from 1, 2, 3 as the numerator, and choose a number from 7, 8, 9 as the denominator, how many fractions can be formed in total.
从1、2、3中选一个数字作分子，从7、8、9中选一个数字作分母，一共可以组成多少个分数．
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<result>9</result>