Do as many 3 sets of anything in 30:00 minutes as you can. The combination does not matter, just change it up and work 3 major or minor muscle groups per session.
Day 1 – 1.5 miles on the treadmill, 75 pushups and 100 overhead lifts with 25 pound weight in 30 minutes.
Day 2 – 1.5 miles on the treadmill, 75 pushups and 150 crunches with 8 pound ball in 30 minutes.
Day 3 – don’t know yet, that is going to be tomorrow.
Right off the bat I see that the number of pushups need to be increased for a 30 minute time period.