Answer:
Natasha fell asleep for 1.125 hours.
Explanation:
We have been given that
Total time spent by Natasha on the beach = 1 1/2 = 3/2 hours
She fell asleep for 3/4 of time she was on the beach.
Hence, the time she fell asleep is given by

Therefore, Natasha fell asleep for 1.125 hours.