Answer:
0.273 = 27.3% probability that she was late on Thursday.
Step-by-step explanation:
On time on Monday, late on Thursday:
Possible outcomes (tuesday-wednesday-thursday).
on time(0.7 probability) - on time(0.7 probability) - late(0.3 probability)
on time(0.7 probability) - late(0.3 probability) - late(0.2 probability)
late(0.3 probability) - on time(0.8 probability) - late(0.3 probability)
late(0.3 probability) - late(0.2 probability) - late(0.2 probability).
What is the probability she was late on Thursday?
Sum of these four outcomes. So
0.273 = 27.3% probability that she was late on Thursday.