A car travels from city A to city B. It takes 1/4 of the whole journey in the first hour and 1/3 of the whole journey in the second hour. It exceeds the midpoint by 15 kilometers. How many kilometers is the distance between cities A and B?
汽车从A城开往B城，第一小时行全程的(1/4)，第二小时行全程的(1/3)，超过中点15千米，A、B两城相距多少千米？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/3) - (1/2)</gadget>
<output>-1/6 = around -0.166667</output>

<gadget id="calculator">(1/4) + (-1/6)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">15 / (1/12)</gadget>
<output>180</output>

<result>180</result>