In one class (2/3) hours, students take up (1/5) of their own research, (1/4) of the teacher's explanation, and the rest is for students to practice. What percentage of the lesson do students practice?
一节课(2/3)小时，学生自主探究占了(1/5)，老师讲解占了(1/4)，其余是学生练习．学生练习占这节课的几分之几？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/5) - (1/4)</gadget>
<output>11/20 = around 0.55</output>

<result>11/20 = around 0.55</result>