A car drives for 3 hours on the first day and 5 hours on the second day, and the first day travels 90 kilometers less than the second day. How many miles per hour on average?
一辆汽车第一天行驶了3小时，第二天行驶了5小时，第一天比第二天少行驶90千米．平均每小时行驶多少千米？
<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">90 / 2</gadget>
<output>45</output>

<result>45</result>