In a science class, the students spent (1/5) hours doing experiments, the teacher spent (3/10) hours lecturing, and the rest of the time students did homework independently. How many hours did the students spend on independent homework?
一堂科学课上，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">3 / 4</gadget>
<output>3/4 = around 0.75</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">(1/5) + (3/10)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(3/4) - (1/2)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>