It takes olivia 12.5 minutes to swim 20 laps around the pool what's olivia's unit rate

Her swimming rate can either be written as 1.6 laps per (one) minute or as 0.625 minutes per lap = 37.5 seconds per (one) lap.
In terms of number of laps per minute, the answer is
20
laps
12.5
minutes
=
1.6
laps per minute.

In terms of the number of minutes per lap, the answer is
12.5
minutes
20
laps
=
5
8
=
0.625
minutes per lap. This is the same as
0.625
min
lap
⋅
60
sec
min
=
37.5
sec
lap

The faster she goes, the more laps she can do in a minute and the fewer minutes (or seconds) it takes her to do one lap.