8.6, 7.9, 8, how many, the average of these 4 numbers is 8.
8.6，7.9，8，多少，这4个数的平均数是8．
<gadget id="calculator">4 * 8</gadget>
<output>32</output>

<gadget id="calculator">32 - 8.6 - 7.9 - 8</gadget>
<output>7.5</output>

<result>7.5</result>