In the mathematics class, the students spent (2/5) hours doing the exercises, and the teacher spent (1/6) less in explaining than the students doing the exercises. How many hours did the teacher explain and the students do the exercises?
数学课上，同学们做练习的时间用了(2/5)小时，老师讲解比同学们做练习少用了(1/6)小时．老师讲解和同学们做练习一共用了多少小时？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(2/5) - (1/6)</gadget>
<output>7/30 = around 0.233333</output>

<gadget id="calculator">(7/30) + (2/5)</gadget>
<output>19/30 = around 0.633333</output>

<result>19/30 = around 0.633333</result>