On the return trip: 16 mph * 3/2 hr = 24 miles, which is 6 miles short of 30 mi.
The distance is 30 miles.
The bird flies all 30 miles in 3/2 hr = 1 and 1/2 hour = 1 hour 30 minutes.
On the return trip, the bird flies 24 miles in 1.5 hours, which is 6 miles short.
