The school organizes students to play. After the school bus leaves, Xiaoxiao is late for some reason. He intercepts a taxi. The driver tells Xiaoxiao that it will take 1 hour and 30 minutes to catch up if he travels 80 kilometers per hour. Kilometers, you can catch up in 42 minutes, find the speed of the school bus.
学校组织同学游玩，校车出发后，小小因故迟到，他拦截一辆的士出租车，司机告诉小小；每小时行80千米，需1小时30分钟才能追上，如果每小时行90千米，42分钟就能追上，求校车的速度．
<gadget id="calculator">80 * 1.5</gadget>
<output>120</output>

<gadget id="calculator">42 / 60</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">90 * (7/10)</gadget>
<output>63</output>

<gadget id="calculator">120 - 63</gadget>
<output>57</output>

<gadget id="calculator">1.5 - (7/10)</gadget>
<output>0.8</output>

<gadget id="calculator">57 / 0.8</gadget>
<output>71.25</output>

<result>71.25</result>