Well!!!!
Watch A loses 1.5 sec/hr
Watch B gains 1 sec/hr
Thus, increase in Time difference between the watches in 1 hr = 2.5 sec
The watches' time are increasung at the rate of 2.5 sec/hr
They will show back the same time if they complete one revolution error
(i.e) when the difference is 1 hr ==> 3600sec
==> TIme for having 3600 sec difference = 3600/2.5 = 1440 hrs = 60 days!!
Thus, the clocks will show same time after 60 days!!!