In a 40-minute physical education class, it took (2/15) hours for warm-up activities, (1/3) hours for the teacher to demonstrate, and the rest of the time for students to be free, how many hours are the students free to play?
一堂40分钟的体育课，做准备活动用了(2/15)小时，老师示范用了(1/3)小时，其余时间学生自由活动，学生自由活动时间是多少小时？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">2 / 15</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(2/3) - (2/15) - (1/3)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>