A book has 160 pages, and Xiaofang has read 70 pages. She can read as many pages as possible to make the remaining pages (1/3) of the pages she has read.
一本书160页，小芳已看70页，她再读多少就能使剩下的是已读页数的(1/3)．
<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">160 * (3/4)</gadget>
<output>120</output>

<gadget id="calculator">120 - 70</gadget>
<output>50</output>

<result>50</result>