A batch of exercise books is distributed to the students in Class 1, Grade 6, with an average of 20 books per person. If only girls are distributed, each person can get 30 books on average. If only boys are distributed, how many books per person can be distributed on average ．
一批练习本分发给六年级一班的学生，平均每人分到20本，若只发给女生，平均每人可分到30本，若只发给男生，平均每人可分到多少本．
<gadget id="calculator">600 / 20</gadget>
<output>30</output>

<gadget id="calculator">600 / 30</gadget>
<output>20</output>

<gadget id="calculator">30 - 20</gadget>
<output>10</output>

<gadget id="calculator">600 / 10</gadget>
<output>60</output>

<result>60</result>