Answer: a)9 3/4 hours
B)1 11/12 hour
Explanation:
Piano: 3 1/2 hour; 3hours 30min
Soccer: 6 1/4 hour; 6hours and 15 min
Telephone: 4 1/3 hour; 4 hours and 20 min.
Remember that in an hour there is 60 min, and 1/2 of an hour is 30 (min), 1/4 is 15(min) and 1/3 is 20(min).
a) 3hours and 30min + 6hours and 15 min
That gives us 9 hours and 45 min, which is 9 3/4 hours.
B) 6hours and 15 min — 4 hours and 20 min
That gives us 1 hour and 55 min, which is 1 11/12 hours.
I hope this helps you!