Answer:
Judy spent 55 min at the gym.
Step-by-step explanation:
From the three people that are listed in the problem Mary is the only one we know the actual time she was at the gym which is 3 h. Sandy on the other hand spent 50 minutes less sprinting than Mary, so we have:
Sandy = Mary - 50 minutes
Sandy = 3h - 50 minutes
Sandy = 3*60 - 50
Sandy = 180 - 50 = 130 minutes
Judy spent 1h and 15 min less than Sandy exercising so we have:
Judy = Sandy - 1h 15min
Judy = 130 min - (60 min + 15 min)
Judy = 130 min - 75 min = 55 min
Judy spent 55 min at the gym.
