When you say "coincide", do you mean when they are "on top of each other?".
If that is what you mean, then:
Every minute on a regular Clock, the hour-hand moves forward 1/2 minute, while the minute-hand moves backwords 5/6 minute.....So, since they are moving towards each other then:
1/2m + 5/6m =60 minutes.
Solve for m and m = 45 minutes(on a regular Clock).
So, the hour-hand will be: 1/2 x 45 =22.5 minutes on your faulty Clock. And:
5/6 x 45 =37.5 minutes (backwards) for the minute-hand. Or: 60 - 37.50 =22.50 when both hands will be on top of each other.
So 45 minutes will have passed on a regular Clock, or the time will be:12:45 pm.