The distance between A and B is 820 kilometers. Car A drives from A to B at a speed of 80 kilometers per hour. After driving for 2 hours, car B drives from B to A at a speed of 85 kilometers per hour. How many hours will it take for the two cars to meet?
甲、乙两地相距820千米，A车从甲开往乙，每小时行驶80千米，开出2小时后，B车才从乙地开往甲地，每小时行驶85千米．两车还要经过多少小时相遇？
<gadget id="calculator">80 * 2</gadget>
<output>160</output>

<gadget id="calculator">820 - 160</gadget>
<output>660</output>

<gadget id="calculator">80 + 85</gadget>
<output>165</output>

<gadget id="calculator">660 / 165</gadget>
<output>4</output>

<result>4</result>