There are 674 books in the book corner of the second class of the third grade, 253 books have been borrowed, and 137 books have been returned. How many books are there in the book corner now?
三年级二班图书角有图书674本，借出了253本，还回了137本，现图书角有多少本图书？
<gadget id="calculator">674 - 253</gadget>
<output>421</output>

<gadget id="calculator">421 + 137</gadget>
<output>558</output>

<result>558</result>