Smiling and reading extracurricular books, I read the whole book (1/10) on the first day, and (1/5) the whole book on the second day. What percentage of this book is left unread?
笑笑看课外书，第一天看全书的(1/10)，第二天看了全书的(1/5)，还剩这本书的几分之几没看？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/10) - (1/5)</gadget>
<output>7/10 = around 0.7</output>

<result>7/10 = around 0.7</result>