Judy spent 1 hour and 15 minutes less than Sandy exercising last week Sandy Sprint 50 minutes less than Mary who's been 3 hours at the gym how long did Judy spend exercising

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.