Middle and senior students listened to the reports given by scientists. There were 84 participants in the middle grades, and the number of participants in the senior grades was three times that of the middle grades. How many people listened to the report?
中、高年级同学听科学家作报告中年级有84人参加，高年级参加的人数是中年级的3倍．听报告的一共有多少人？
<gadget id="calculator">84 * 3</gadget>
<output>252</output>

<gadget id="calculator">252 + 84</gadget>
<output>336</output>

<result>336</result>