Chapter 4.3, Problem 31ES

To determine

To calculate: The amount of time Richard spends driving on country roads and on the interstate highway provided that he commutes to work by first driving on country roads at an average speed of $45$ miles per hour and then drives on the interstate highway at an average speed of $75$ miles per hour and his total commuting distance is $42$ miles and his total commuting time is $0.6$ hours.