Cars A and B drive from cities A and B respectively, meet each other after 5 hours, and then drive forward for 2 hours. At this time, car A is still 210 kilometers away from city B, and car B is still 210 kilometers away from city A. 300 kilometers. What is the distance in kilometers between cities A and B?
甲、乙两车分别从A、B两城相对开出，5小时后相遇，然后又各自向前行驶2小时，这时甲车距B城还有210千米，乙车距A城还有300千米．求A、B两城相距多少千米？
<gadget id="calculator">210 + 300</gadget>
<output>510</output>

<gadget id="calculator">5 - 2</gadget>
<output>3</output>

<gadget id="calculator">510 / 3</gadget>
<output>170</output>

<gadget id="calculator">170 * 5</gadget>
<output>850</output>

<result>850</result>