Cars A and B drive opposite each other from places A and B at the same time. They meet each other in 4 hours. When they meet, car A travels 50 kilometers less than car B. The speed ratio of cars A and B is 5:7. Find places A and B distance.
甲、乙两车同时从A、B两地相对开车，4小时相遇，相遇时，甲车比乙车少行50千米，甲乙两车的速度比是5：7，求A、B两地的距离．
<gadget id="calculator">7 - 5</gadget>
<output>2</output>

<gadget id="calculator">50 / 2</gadget>
<output>25</output>

<gadget id="calculator">5 + 7</gadget>
<output>12</output>

<gadget id="calculator">25 * 12</gadget>
<output>300</output>

<result>300</result>