Arrange the five numbers from small to large, the average number is 42, the average number of the first three numbers is 40, and the sum of the last three numbers is 140, so what is the middle number?
把五个数从小到大排列，其平均数是42，前三个数的平均数是40，后三个数的和是140，那么中间一个数是多少？
<gadget id="calculator">40 * 3</gadget>
<output>120</output>

<gadget id="calculator">42 * 5</gadget>
<output>210</output>

<gadget id="calculator">140 - 210</gadget>
<output>-70</output>

<gadget id="calculator">120 + (-70)</gadget>
<output>50</output>

<result>50</result>