What is the number that is obtained after subtracting 7 from a certain number and then multiplying it by 7?
某数减去7剩下的再乘以7，所得的结果与先减去11剩下的再乘以11的结果相同，这个数是多少．
<gadget id="calculator">11 * 11</gadget>
<output>121</output>

<gadget id="calculator">7 * 7</gadget>
<output>49</output>

<gadget id="calculator">121 - 49</gadget>
<output>72</output>

<gadget id="calculator">11 - 7</gadget>
<output>4</output>

<gadget id="calculator">72 / 4</gadget>
<output>18</output>

<result>18</result>