In Xinghua Elementary School, the music group accounted for 2/35 of the extracurricular interest group, the art group accounted for 2/7, and the instrumental music group was equal to the sum of the two groups. What percentage of the total number of people are in the instrumental music group?
兴华小学参加音乐组的人数占课外兴趣小组人数的(2/35)，美术组的人数占(2/7)，器乐组的人数等于这两个组人数的总和．器乐组的人数占总人数的几分之几？
<gadget id="calculator">2 / 35</gadget>
<output>2/35 = around 0.057143</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(2/35) + (2/7)</gadget>
<output>12/35 = around 0.342857</output>

<result>12/35 = around 0.342857</result>