20 is 2.4 less than 8 times of a number, so find this number.
20比一个数的8倍少2.4，求的这个数．
<gadget id="calculator">20 + 2.4</gadget>
<output>22.4</output>

<gadget id="calculator">22.4 / 8</gadget>
<output>2.8</output>

<result>2.8</result>