Congcong reads a 100-page book. He reads (1/10) of it on the first day and (1/5) of it on the second day. How much of it is left?
聪聪看一本100页的书，第一天看了它的(1/10)，第二天看了它的(1/5)，还剩几分之几没有看？
<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">(1/10) + (1/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

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