If the average of the five numbers 1, 2, x, 4, and 5 is 10, what is x?
如果1、2、x、4、5这5个数的平均数是10，那么x是多少．
<gadget id="calculator">10 * 5</gadget>
<output>50</output>

<gadget id="calculator">50 - 1 - 2 - 4 - 5</gadget>
<output>38</output>

<result>38</result>