Cars A and B are driving towards each other at two places 270 kilometers apart at the same time. Car A travels 40 kilometers per hour. After 3 hours, the distance between Car A and Car B is 30 kilometers. How many kilometers does Car B travel per hour? (solution by equation)
甲乙两车在相距270千米的两地同时相向而行，甲车每小时行40千米，经过3小时与乙车相距30千米，求乙车每小时行多少千米？(用方程解)
<gadget id="calculator">40 * 3</gadget>
<output>120</output>

<gadget id="calculator">270 - 120 - 30</gadget>
<output>120</output>

<gadget id="calculator">120 / 3</gadget>
<output>40</output>

<result>40</result>