There are 84 students in the fourth grade of Qingquan Primary School, three times the number in the sixth grade, and half the number in the first grade. How many students are there in the sixth grade and the first grade?
清泉小学四年级有学生84人，六年级是四年级的3倍，一年级是四年级的一半，六年级和一年级共有多少人？
<gadget id="calculator">84 * 3</gadget>
<output>252</output>

<gadget id="calculator">84 / 2</gadget>
<output>42</output>

<gadget id="calculator">252 + 42</gadget>
<output>294</output>

<result>294</result>