Most of the students in Class 4 and 2 actively participated in extracurricular interest groups. There are (4/15) students participating in the art group activities, more than the calligraphy group (1/15). How many students did not participate in these two groups?
四2班大部分同学积极参加课外兴趣小组．有(4/15)的同学参加美术组活动，比书法小组多(1/15)．还有几分之几的同学没有参加这两个小组？
<gadget id="calculator">4 / 15</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(4/15) - (1/15)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (4/15) - (1/5)</gadget>
<output>8/15 = around 0.533333</output>

<result>8/15 = around 0.533333</result>