A highway, 25% of the total length is repaired on the first day, and 20% of the total length is repaired on the second day. At this time, there are still 24 kilometers away from the midpoint. How many kilometers will be repaired on the first day?
一条公路，第一天修全长25%，第二天修全长20%，这时离中点还有24千米，第一天修多少千米？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/2) - (1/4) - (1/5)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">24 / (1/20)</gadget>
<output>480</output>

<result>480</result>