There is a batch of books divided into three groups, and each person gets exactly 15 books on average; if only the first group is distributed, then each person gets 35 books; if only the second group is distributed, then each person gets 42 books; if It is only distributed to the third group, so how many copies can each person get.
有一批书分给三个组，平均每人正好分15本；如果只分给第一组，那么每人分到35本；如果只分给第二组，那么每人分到42本；如果只分给第三组，那么每人可以分到多少本．
<gadget id="calculator">15 / 35</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">15 / 42</gadget>
<output>5/14 = around 0.357143</output>

<gadget id="calculator">1 - (3/7) - (5/14)</gadget>
<output>3/14 = around 0.214286</output>

<gadget id="calculator">15 / (3/14)</gadget>
<output>70</output>

<result>70</result>