That would be (4/6) of 45 minutes, or 180/6 minutes, or 30 minutes.
You could also find her rate: 6 miles / 45 minutes, or 8 miles / 60 minutes.
Write an equation of ratios:
8 mi 4 mi
---------- = ------------
60 min x
Solving for x: 8x = 240; x = 30 minutes
