Add 7 to a number, multiply by 7, subtract 7, divide by 7, the result is still 7, do you know what this number is?
把一个数加上7，乘上7，减去7，除以7，结果还是7，你知道这个数是多少吗？
<gadget id="calculator">7 * 7</gadget>
<output>49</output>

<gadget id="calculator">49 + 7</gadget>
<output>56</output>

<gadget id="calculator">56 / 7</gadget>
<output>8</output>

<gadget id="calculator">8 - 7</gadget>
<output>1</output>

<result>1</result>