Among the 13 people, there are 9 people who like to play table tennis, 7 people who like to play basketball, and 4 people who like to play both table tennis and basketball. How many people don’t like to play table tennis and don’t like to play basketball? people.
在13人中，爱打乒乓球的有9人，爱打篮球的有7人，既爱打乒乓球又爱打篮球的有4人，那么不爱打乒乓球且不爱打篮球的有多少人．
<gadget id="calculator">7 - 4</gadget>
<output>3</output>

<gadget id="calculator">9 + 3</gadget>
<output>12</output>

<gadget id="calculator">13 - 12</gadget>
<output>1</output>

<result>1</result>