The distance between A and B is 915 kilometers. A train travels from A to B. After 3 hours, B train travels from B to A. It is known that A travels 80 kilometers per hour, and B travels 70 kilometers per hour. km. How many hours does car B meet car A?
A、B两地相距915千米，甲火车从A地开往B地，3小时后乙火车从B地开往A地，已知甲车每小时行80千米，乙车每小时行70千米．乙车开出几小时后与甲车相遇？
<gadget id="calculator">80 * 3</gadget>
<output>240</output>

<gadget id="calculator">915 - 240</gadget>
<output>675</output>

<gadget id="calculator">80 + 70</gadget>
<output>150</output>

<gadget id="calculator">675 / 150</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>