Sixth grade students join interest groups, half of them 5 people join mathematics interest groups, the remaining half 12 people join Chinese interest groups, and there are 30 students left, ask how many people participate in interest groups.
六年级同学参加兴趣小组，其中一半又5人参加数学兴趣小组，余下的一半又12人参加语文兴趣小组，还剩下30人，问参加兴趣小组的有多少人．
<gadget id="calculator">30 + 12</gadget>
<output>42</output>

<gadget id="calculator">42 * 2</gadget>
<output>84</output>

<gadget id="calculator">84 + 5</gadget>
<output>89</output>

<gadget id="calculator">89 * 2</gadget>
<output>178</output>

<result>178</result>