Two cars, fast and slow, drive toward each other from places A and B at the same time, and continue to move forward after meeting. When the distance between the two cars is 280 km, the fast car has traveled the whole distance (3/4), and the slow car has traveled the whole distance (3/5). How many kilometers are there between the two cities?
快慢两车同时从甲、乙两地相向而行，相遇后继续前进，当两车相距280km时，快车行了全程的(3/4)，慢车行了全程的(3/5)．甲乙两城相距多少km？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">3 / 5</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">(3/4) + (-2/5)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">280 / (7/20)</gadget>
<output>800</output>

<result>800</result>