There are a total of 210 books in the book corner of Class 4 and Class 3. On the first day, 1/7 of the total was borrowed, and on the second day, 2/21 of the total was borrowed. How many books were borrowed in two days?
四3班的图书角共放有图书210本，第一天借出了总数的(1/7)，第二天借出了总数的(2/21)．两天一共借出了多少本图书？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">2 / 21</gadget>
<output>2/21 = around 0.095238</output>

<gadget id="calculator">(1/7) + (2/21)</gadget>
<output>5/21 = around 0.238095</output>

<gadget id="calculator">210 * (5/21)</gadget>
<output>50</output>

<result>50</result>