We know that the second man was shooting four minutes longer than the first one and 3 min less than the the third one. All shooting time was less than an hour.

I think that we can consider that all shooting time is equal to the time of the third shooter, because he was training 7 minutes more comparing to the first and 3 min more comparing with the second. But the main problem, I suppose, is that we don't know exact time of how much they trained for. Just less than an hour. So perhaps I should make an inequality, but I'm not sure. Any help would be apreciated. Thanks!