A and B have the same number of books. After removing 18 books from A bookshelf and 42 books from B bookshelf, the remaining books in A bookshelf are 4 times the remaining books in B bookshelf. So how many books are originally placed in the two bookshelves of A and B?
甲、乙两个书架中摆放的书一样多，从甲书架中拿走18本，从乙书架中拿走42本后，甲书架中余下的书是乙书架中余下的书的4倍．则甲、乙两个书架中原来共摆放多少本书．
<gadget id="calculator">4 * 42</gadget>
<output>168</output>

<gadget id="calculator">168 - 18</gadget>
<output>150</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">150 / 3</gadget>
<output>50</output>

<gadget id="calculator">50 + 50</gadget>
<output>100</output>

<result>100</result>