Class 1 of the third year has 9 students who like to eat apples, 8 students who like to eat oranges, and 4 students who like to eat both kinds of fruits. How many people in total like to eat apples and oranges?
三年一班同学喜欢吃苹果的有9人，喜欢吃橘子的有8人，这两种水果都喜欢吃有4人，喜欢吃苹果、橘子的一共有多少人．
<gadget id="calculator">8 - 4</gadget>
<output>4</output>

<gadget id="calculator">9 + 4</gadget>
<output>13</output>

<result>13</result>