Add 6 to a number, divide by 2, subtract 9, and finally get 8. Find this number.
一个数加上6，除以2，再减去9，最后得8，求这个数．
<gadget id="calculator">8 + 9</gadget>
<output>17</output>

<gadget id="calculator">17 * 2</gadget>
<output>34</output>

<gadget id="calculator">34 - 6</gadget>
<output>28</output>

<result>28</result>