There are seven different numbers, the largest number is 28 more than the smallest number, and the average of the seven numbers is 21. If the largest and smallest numbers are removed, the average of the remaining numbers is 19. What is the smallest number among these seven numbers?
有七个不同的数，最大的数比最小的数多28，七个数的平均数是21．如果去掉最大的和最小的数，剩下的数的平均数是19．这七个数中最小的一个数是多少．
<gadget id="calculator">21 * 7</gadget>
<output>147</output>

<gadget id="calculator">7 - 2</gadget>
<output>5</output>

<gadget id="calculator">19 * 5</gadget>
<output>95</output>

<gadget id="calculator">147 - 95 - 28</gadget>
<output>24</output>

<gadget id="calculator">24 / 2</gadget>
<output>12</output>

<result>12</result>