It takes 5 hours for a passenger car to travel from A to B, and 7 hours for a truck to complete the journey. The two cars depart from A and B respectively and drive in opposite directions at the same time. After 2 hours, the distance between the two cars is 198 kilometers. How many kilometers does the truck travel per hour?
客车从甲到乙要5小时，货车行完全程7小时，两车分别从甲乙出发，同时对行，2小时后两车相距198千米，货车每小时行几千米？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(1/5) + (1/7)</gadget>
<output>12/35 = around 0.342857</output>

<gadget id="calculator">(12/35) * 2</gadget>
<output>24/35 = around 0.685714</output>

<gadget id="calculator">1 - (24/35)</gadget>
<output>11/35 = around 0.314286</output>

<gadget id="calculator">198 / (11/35) / 7</gadget>
<output>90</output>

<result>90</result>