Cars A and B start from the same place at the same time and drive in opposite directions. After 3 hours, the distance between them is 270 kilometers. The speed of car A is 42 km/h, find the speed of car B.
甲、乙两辆汽车同时从同一地点出发，相背而行，3小时后相距270千米．甲车的速度是42千米/时，求乙车的速度．
<gadget id="calculator">270 / 3</gadget>
<output>90</output>

<gadget id="calculator">90 - 42</gadget>
<output>48</output>

<result>48</result>