Among the 30 students, 8 learn French, 12 learn Spanish, and 3 learn both French and Spanish. Q: How many students do not learn both languages.
30名学生中，8人学法语，12人学西班牙语，3人既学法语又学西班牙语．问：有多少名学生两种语言都不学．
<gadget id="calculator">8 + 12</gadget>
<output>20</output>

<gadget id="calculator">20 - 3</gadget>
<output>17</output>

<gadget id="calculator">30 - 17</gadget>
<output>13</output>

<result>13</result>