Two trains, A and B, depart from opposite sides of the two cities 660 kilometers apart. Train A travels 60 kilometers per hour, and train B travels 70 kilometers per hour. Train B leaves first and then train A departs 2 hours later. After how many hours did the two cars meet?
甲、乙两列火车从相距660千米的两城相向开出，甲车每小时行60千米，乙车每小时行70千米，乙车先开出2小时后，甲车才出发，经过几小时两车相遇？
<gadget id="calculator">70 * 2</gadget>
<output>140</output>

<gadget id="calculator">660 - 140</gadget>
<output>520</output>

<gadget id="calculator">60 + 70</gadget>
<output>130</output>

<gadget id="calculator">520 / 130</gadget>
<output>4</output>

<result>4</result>