In the first quarter of this year, the school used 3000 kilowatt-hours of electricity, 20% less than in the second quarter. How much electricity did the school use in the first half of this year?
学校今年第一季度用电3000度，比第二季度少用20%，学校今年前半年用电多少度？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">3_000 / (4/5)</gadget>
<output>3_750</output>

<gadget id="calculator">3_750 + 3_000</gadget>
<output>6_750</output>

<result>6_750</result>