There is a number that is so strange that the product of subtracting 7 and multiplying 7 by 7 is equal to the result of subtracting 11 and multiplying by 11. Find this number.
有个数真奇怪，它减去7的差再乘7所得的积与它减去11的差乘11的结果相等．求这个数．
<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>