Using two of the three numbers 7, 8, and 9 as factors, how many different products can be calculated.
用7、8、9三个数中的两个作为因数，可以算出多少个不同的积来．
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">2 / 2</gadget>
<output>1</output>

<gadget id="calculator">3 * 1</gadget>
<output>3</output>

<result>3</result>