The third grade students go to the autumn outing by car. There are 8 cars in total, and each car holds 42 people. The first 7 cars are all full, and the eighth car still has 15 vacancies. How many people will participate in the autumn outing?
三年级同学乘车去秋游，一共有8辆车，每辆车乘42人，前7辆车全部乘满，第八辆车还有15个空位，总共有多少人参加秋游？
<gadget id="calculator">42 * 7</gadget>
<output>294</output>

<gadget id="calculator">42 - 15</gadget>
<output>27</output>

<gadget id="calculator">294 + 27</gadget>
<output>321</output>

<result>321</result>