Xiao Ming is reading "Fun Mathematics". He read the whole book on the first day (4/15) and the whole book on the second day (7/15). How much of it is left?
小明正在看一本《趣味数学》，第一天看了全书的(4/15)，第二天看了全书的(7/15)，还剩几分之几没看？
<gadget id="calculator">4 / 15</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">7 / 15</gadget>
<output>7/15 = around 0.466667</output>

<gadget id="calculator">1 - (4/15) - (7/15)</gadget>
<output>4/15 = around 0.266667</output>

<result>4/15 = around 0.266667</result>