There are 36 students in a class taking a test, 25 of them answered the first question correctly, 23 of them answered the second question correctly, and 15 of them answered both questions correctly. How many students are asked to answer both questions incorrectly?
某班有36个同学参加一项测试，答对第一题的有25人，答对第二题的有23人，两题都答对的有15人．问多少个同学两题都答得不对？
<gadget id="calculator">25 - 15</gadget>
<output>10</output>

<gadget id="calculator">23 + 10</gadget>
<output>33</output>

<gadget id="calculator">36 - 33</gadget>
<output>3</output>

<result>3</result>