There are 59 students in a certain grade participating in the sports interest class, among which 42 students participate in the basketball class, and 28 students participate in the table tennis class. How many students participate in both sports?
某年级有59名同学参加体育兴趣班，其中有42人参加篮球班，有28人参加乒乓球班，有多少人两种项目都参加？
<gadget id="calculator">28 - 59</gadget>
<output>-31</output>

<gadget id="calculator">42 + (-31)</gadget>
<output>11</output>

<result>11</result>