A passenger car and a truck depart from A and B in opposite directions at the same time and meet at a place 15 kilometers away from the midpoint. It is known that the speed ratio of passenger cars and trucks is 4:3. How many kilometers are there between A and B?
一辆客车和一辆货车同时从甲乙两地相向开出，在离中点15千米的地方相遇．已知客车与货车的速度比是4：3．求甲乙两地相距多少千米？
<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

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

<gadget id="calculator">(4/7) - (1/2)</gadget>
<output>1/14 = around 0.071429</output>

<gadget id="calculator">15 / (1/14)</gadget>
<output>210</output>

<result>210</result>