Sarah read 4 books in 2 h 6 min. She took the same amount of time to read each of the first 3 books. She took 46 min longer to read the fourth book than each of the first 3 books. She finished reading all the books at 22 21. What time did she start reading the fourth book?
Duration that Sarah took to read the first book = 1 u
Duration that Sarah took to read the second book = 1 u
Duration that Sarah took to read the third book = 1 u
Duration that Sarah took to read the fourth book = 1 u + 46 min

Total duration that Sarah took to read the four books 
= 1 u + 1 u + 1 u + 1 u + 46 min
= 4 u + 46 min

4 u + 46 min = 2 h 6 min
4 u = 126 min - 46 min
4 u = 80 min  

1 u = 80 min ÷ 4 = 20 min

Duration that Sarah took to read the fourth book
= 20 min + 46 min
= 66 min
= 1 h 6 min

1 h 6 min before 22 21: 21 15

Time that Sarah started to read the fourth book = 21 15

Answer(s): 21 15