Cars A and B leave opposite places A and B at the same time, and move back and forth between the two places. It is known that at a distance of 50 kilometers from place A, two cars meet for the first time, and at a distance of 30 kilometers from place B, the two cars meet for the second time. How many kilometers is the distance between places A and B?
甲、乙两车同时从A、B两地相对开出，并在两地往返运动．已知在距离A地50千米，两车第一次相遇，在距离B地30千米，两车第二次相遇，问A、B两地相距多少千米？
<gadget id="calculator">50 * 3</gadget>
<output>150</output>

<gadget id="calculator">150 - 30</gadget>
<output>120</output>

<result>120</result>