The fourth grade students participated in the garden activities. There were 15 people in the first group, 18 people in the second ancestor, 9 people in the third group, and 12 people in the other three groups. How many students are there on average in each group participating in the garden tour?
四年级的同学参加游园活动，一组有15人，二祖有18人，三组有9人，其余的3组都有12人．参加游园活动的同学平均每组有多少人？
<gadget id="calculator">12 * 3</gadget>
<output>36</output>

<gadget id="calculator">15 + 18 + 9 + 36</gadget>
<output>78</output>

<gadget id="calculator">78 / 6</gadget>
<output>13</output>

<result>13</result>