A truck travels from city A to city B at a speed of 45 kilometers per hour. Three hours after it started, another light car set off from city B to city A, which was 15 kilometers faster than the truck per hour. If the distance between the two cities is 345 kilometers, how many hours can the light vehicle meet the truck after departure?
载重汽车以每小时45千米的速度自A城开往B城．它出发了3小时后另有一辆轻便汽车自B城出发往A城，它每小时比载重汽车快15千米．若两城相距345千米，轻便汽车出发几小时后可与载重汽车相遇？
<gadget id="calculator">45 * 3</gadget>
<output>135</output>

<gadget id="calculator">345 - 135</gadget>
<output>210</output>

<gadget id="calculator">45 + 15 + 45</gadget>
<output>105</output>

<gadget id="calculator">210 / 105</gadget>
<output>2</output>

<result>2</result>