Peter painted a total of 3 rooms. He spent 1/5 of his time on the first room and 1/3 of the remaining time on the second room. He spent 8 hours painting the last room. How much time did he take to complete painting all 3 rooms?
Call the total time = T
First room = (1/5)T
Second room = (T - 1/5 T) (1/3) = (4/5)T (1/3) = (4/15)T
Third room = 8
So
(1/5)T + (4/15)T + 8 = T
(7/15)T + 8 = T
8 = T - (7/15)T
8 = (8/15)T
T = 8 ( 15/8) = 15 hours
+77 
