Answer:
57 minutes
Explanation:
First, add 75 minutes to the time he started the test. Then, subtract the time you get from the time for his dentist appointment.
75 minutes is the same as 1 hour 15 minutes (1 hour = 60 minutes)
H M
2 : 18
+ 1 : 15
3 : 33
He ended the test by 3:33 PM.
H M
4 : 30
- 3 : 33
0 : 57
Therefore, he had 57 minutes between the end of the test and his appointment.