The expression for the total time is:
T = (324/34x).
He does 18 laps in total.
The average rate for the whole 18 laps is the average of the rates (taking in account the number of laps made with each) so we get:
average rate = (8/18)*3x + (10/18)*x = (34x/18)
This means that he does (34x/18) laps per hour.
Then, the time needed to do 18 laps is:
T = (18/(34x/18)) = (324/34x).
If you want to learn more about rates:
https://brainly.com/question/843074
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