In a 40-minute class, Mr. Zhang spent (2/5) hours organizing students to study, (1/10) hours for feedback exercises, and the rest of the time to complete the homework independently. How much time did the students spend on completing the homework independently?
一节课40分钟，张老师用了(2/5)小时组织学生学习，反馈练习用了(1/10)小时，剩下的时间独立完成作业，学生独立完成作业用了多少时间？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(2/5) + (1/10)</gadget>
<output>1/2 = around 0.5</output>

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

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