A and B start from two places A and B that are 180km apart. A rides a bicycle and B rides a motorcycle. They go towards each other along a road along the river. A's speed is 15 km/h, while B's speed is 45 km / hour, if A first drives for 2 hours before B starts, how long will it take for the two to meet?
甲、乙两人从相距180km的A、B两地出发，甲骑自行车，乙骑摩托车，沿河一条路相向而行，甲的速度是15千米/时，乙的速度是45千米/时，如果甲先行驶2小时后乙才出发，再过多少时间两人相遇？
<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<gadget id="calculator">180 - 30</gadget>
<output>150</output>

<gadget id="calculator">15 + 45</gadget>
<output>60</output>

<gadget id="calculator">150 / 60</gadget>
<output>5/2 = around 2.5</output>

<result>5/2 = around 2.5</result>