teaching class lasts 40 minutes, the students spend (1/5) hours doing experiments, the teacher spends (3/10) hours lecturing, and the rest of the time students do homework independently. How many hours did the students spend on independent homework?
一堂教学课40分钟，学生动手做实验用了(1/5)小时，老师讲课用了(3/10)小时，其余的时间学生独立做作业．学生独立做作业用了多少小时？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

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

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(2/3) - (1/5) - (3/10)</gadget>
<output>1/6 = around 0.166667</output>

<result>1/6 = around 0.166667</result>