8 people in class 31 subscribed to "Mickey Mouse", 7 people subscribed to "We Love Science", 3 people subscribed to both publications, how many people in class 31 subscribed to the publications?
三1班有8人订了《米老鼠》，7人订了《我们爱科学》，两种刊物都订了的有3人，三1班共有多少人订了刊物．
<gadget id="calculator">8 + 7</gadget>
<output>15</output>

<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<result>12</result>