The distance between A and B is 189 kilometers. An express train travels 72 kilometers per hour from A to B, and a slow train travels 54 kilometers per hour from B to A. If two cars start at the same time, how many hours later will the two cars meet? (List equations and solve)
甲乙两地相距189千米，一列快车从甲地开往乙地每小时行72千米，一列慢车从乙地开往甲地每小时行54千米．若两车同时出发，几小时后两车相遇？(列方程并求解)
<gadget id="calculator">72 + 54</gadget>
<output>126</output>

<gadget id="calculator">189 / 126</gadget>
<output>3/2 = around 1.5</output>

<result>3/2 = around 1.5</result>