There are 40 students in a certain class, 15 of them participate in the mathematics group, 18 participate in the model group, and 10 participate in both groups, so how many students do not participate in both groups?
某班有40名学生，其中15名参加数学小组，18人参加航模小组，有10人两个小组都参加，那么有多少人两个小组都不参加．
<gadget id="calculator">15 - 10</gadget>
<output>5</output>

<gadget id="calculator">18 + 5</gadget>
<output>23</output>

<gadget id="calculator">40 - 23</gadget>
<output>17</output>

<result>17</result>