The teacher distributes some exercise books to the students in 3 groups. If only for the first group, each student can get 12 books; if only for the second group, each student can get 15 books; if only for the third group, each student can get 20 books ． Then, distribute these exercise books to 3 groups at the same time, how many books can each student get on average?
老师将一些练习本分给3个小组的同学．如果只分给第一小组，每个同学能分到12本；如果只分给第二小组，每个同学能分到15本；如果只分给第三小组，每个同学能分到20本．那么，把这些练习本同时分给3个小组，平均每个同学能分到多少本？
<gadget id="calculator">60 / 12</gadget>
<output>5</output>

<gadget id="calculator">60 / 15</gadget>
<output>4</output>

<gadget id="calculator">60 / 20</gadget>
<output>3</output>

<gadget id="calculator">5 + 4 + 3</gadget>
<output>12</output>

<result>5</result>