Kylie read 4 books in 1 h 42 min. She took the same amount of time to read each of the first 3 books. She took 50 min longer to read the fourth book than each of the first 3 books. She finished reading all the books at 20 39. What time did she start reading the fourth book?
Duration that Kylie took to read the first book = 1 u
Duration that Kylie took to read the second book = 1 u
Duration that Kylie took to read the third book = 1 u
Duration that Kylie took to read the fourth book = 1 u + 50 min

Total duration that Kylie took to read the four books 
= 1 u + 1 u + 1 u + 1 u + 50 min
= 4 u + 50 min

4 u + 50 min = 1 h 42 min
4 u = 102 min - 50 min
4 u = 52 min  

1 u = 52 min ÷ 4 = 13 min

Duration that Kylie took to read the fourth book
= 13 min + 50 min
= 63 min
= 1 h 3 min

1 h 3 min before 20 39: 19 36

Time that Kylie started to read the fourth book = 19 36

Answer(s): 19 36