There are 40 students in the second class of the fifth grade, 25 of them did not participate in the mathematics group, 18 participated in the aircraft model group, and 10 participated in both groups. So how many students in total participated in only one of the two groups?
五年级二班有40名同学，其中有25：人没参加数学小组，有18人参加航模小组，有10人两个小组都参加．那么只参加了这两个小组之一的学生共有多少人？
<gadget id="calculator">40 - 25 - 10</gadget>
<output>5</output>

<gadget id="calculator">18 - 10</gadget>
<output>8</output>

<gadget id="calculator">5 + 8</gadget>
<output>13</output>

<result>13</result>