Two cars depart from Station A and Station B in opposite directions. To complete the journey, the truck takes 6 hours and the bus takes 9 hours. After 2 hours, the two cars are still 120 kilometers apart. How much does the bus travel per hour? km?
两辆汽车分别从甲、乙两站相向开出，若要行完全程，货车需要6小时，客车需要9小时，开出2小时后，两车还相距120千米，问客车每小时行多少千米？
<gadget id="calculator">2 / 6</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">1 - (1/3) - (2/9)</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">120 / (4/9)</gadget>
<output>270</output>

<gadget id="calculator">270 / 9</gadget>
<output>30</output>

<result>30</result>