There are some books that are distributed evenly to the whole class, and each person gets 12 books. If they are only distributed to girls, each person can get 20 books. How many books can each person get if they are only distributed to boys?
有一些书，平均分给全班，每人分到12本，如果只分给女生，每人可分到20本．如果只发给男生每人可得多少本．
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/12) - (1/20)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / (1/30)</gadget>
<output>30</output>

<result>30</result>