A certain number is divided by 5, subtracted 10, multiplied by 2, and finally added 20, the result is equal to 40, what is this number?
某数除以5，减去10，再乘2，最后加上20，结果等于40，这个数是多少．
<gadget id="calculator">40 - 20</gadget>
<output>20</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 + 10</gadget>
<output>20</output>

<gadget id="calculator">20 * 5</gadget>
<output>100</output>

<result>100</result>