Hello there, and thank you for posting your question here on brainly.
You can calculate this by finding out how much 1/4th of an hour is.
1/4 =.25
.25 of 60 is 20.
From here you can multiply 8 by four.
8 * 4 = 24.
The swimmer does 24 laps per hour.
Hope this helped!! ☺♥
