The ratio of the number of boys to girls in the fourth grade is 7:5, and there are 70 fewer girls than boys. How many people are there in the fourth grade?
四年级男生和女生人数的比是7：5，女生比男生少70人．四年级一共有多少人？
<gadget id="calculator">7 - 5</gadget>
<output>2</output>

<gadget id="calculator">70 / 2</gadget>
<output>35</output>

<gadget id="calculator">7 + 5</gadget>
<output>12</output>

<gadget id="calculator">35 * 12</gadget>
<output>420</output>

<result>420</result>