The sixth grade of Qingqingcaoyuan Primary School held a Chinese and mathematics competition. The number of people who participated in the math competition accounted for 80% of the total number of the whole grade, and those who participated in the Chinese competition accounted for 60% of the number of people who participated in the competition. There were 30 students who participated in both subjects. How many people participated in the whole grade people.
青青草园小学六年级举行语文和数学竞赛，参加数学竞赛的人数占全年级总人数的80%，参加语文竞赛的占竞赛人数的60%，两科都参加的有30人，全年级共有多少人．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">60 / 100</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(3/5) - 1</gadget>
<output>-2/5 = around -0.4</output>

<gadget id="calculator">(4/5) + (-2/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">30 / (2/5)</gadget>
<output>75</output>

<result>75</result>