Two cars, passenger and freight, are driving toward each other at places A and B, which are 450 kilometers apart. The passenger car travels 80 kilometers per hour. After 3 hours, the distance between the truck and the truck is 30 kilometers. How many kilometers per hour does the truck travel?
客、货两车在相距450千米的A、B两地同时相向而行，客车每小时行80千米，经过3小时与货车相距30千米，求货车每小时行多少千米？
<gadget id="calculator">480 / 3</gadget>
<output>160</output>

<gadget id="calculator">160 - 80</gadget>
<output>80</output>

<result>80</result>