From city A to city B, the express train travels 80 kilometers per hour and can be reached in 3 hours. It takes an extra hour for the slow train to arrive. How many kilometers per hour does the slow car travel?
从甲城市到乙城市，快车每小时行80千米，3小时可以到达．慢车要多用1小时才能到达．慢车每小时行多少千米？
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">80 * (3/4)</gadget>
<output>60</output>

<result>60</result>