Xiao Ming reads a book. I watched it (2/7) on the first day, and (1/5) on the second day, how many of them didn’t watch it?
小明看一本书．第一天看了它的(2/7)，第二天看了它的(1/5)，还剩几分之几没有看？
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

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

<gadget id="calculator">1 - (2/7) - (1/5)</gadget>
<output>18/35 = around 0.514286</output>

<result>18/35 = around 0.514286</result>