The teacher wrote several consecutive natural numbers starting from 11 on the blackboard, and later erased one of the numbers. The average of the remaining numbers is (309/13), so what is the erased natural number?
老师在黑板上写了从11开始的若干个连续自然数，后来擦掉了其中一个数，剩下的数的平均数是(309/13)，那么擦掉的那个自然数是多少．
<gadget id="calculator">11 + 37</gadget>
<output>48</output>

<gadget id="calculator">27 / 2</gadget>
<output>27/2 = around 13.5</output>

<gadget id="calculator">48 * (27/2)</gadget>
<output>648</output>

<gadget id="calculator">309 / 13</gadget>
<output>309/13 = around 23.769231</output>

<gadget id="calculator">26 * (309/13)</gadget>
<output>618</output>

<gadget id="calculator">648 - 618</gadget>
<output>30</output>

<result>30</result>