Question 981631
15 minutes is what portion of an hour?  15/60 = 1/4.  One of the painters must take 4 hours.  That leaves a whole hour left.  Any combination that can equal a whole works.
For instance, let's assume that Andrew takes 4 hours (for all cases since we need a quarter hour.)  
If A = 1/4, and B = 0, then C = 1/1 (total of 1 1/4 hours)
If A = 1/4, and B = 1/1, then C = 0 (not everyone is in agreement that 0 is an integer)
If A = 1/4, and B = 2, then C = 2 (1/4 + 1/2 + 1/2 = 1 1/4)
Are there any other WHOLE numbers?  I didn't find any.  Of course, any of them can be the 4 hours...