30 contestants participated in the environmental protection knowledge competition organized by the school. They won the first, second and third prizes respectively. Among them, the number of first and second prizes accounted for (2/5) of the total number of people, and the number of second and third prizes accounted for ( 5/6), how many people won the second prize.
30名选手参加学校组织的环保知识竞赛，他们分别获得一，二，三等奖，其中一，二等奖人数占总人数的(2/5)，二，三等奖人数占总人数的(5/6)，获得二等奖的有多少人．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">5 / 6</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">(5/6) - 1</gadget>
<output>-1/6 = around -0.166667</output>

<gadget id="calculator">(2/5) + (-1/6)</gadget>
<output>7/30 = around 0.233333</output>

<gadget id="calculator">30 * (7/30)</gadget>
<output>7</output>

<result>7</result>