There is a two-layer bookshelf. It is known that the number of books on the upper shelf is three times that of the lower shelf. If the number of books on the upper shelf increases by 50 and the number of books on the lower shelf increases by 80, then the number of books on the upper shelf is twice that of the lower shelf. ． How many books are there in the upper bookshelf?
有一个两层书架，已知上层书架上的存书是下层书架的3倍，如果上层书架的书增加50本，下层书架的书增加80本，那么上层书架的存书是下层书架的2倍．求原来上层书架有多少本书？
<gadget id="calculator">80 * 2</gadget>
<output>160</output>

<gadget id="calculator">160 - 50</gadget>
<output>110</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/3) * 2</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">110 / (1/3)</gadget>
<output>330</output>

<result>330</result>