Linda read 4 books in 2 h. She took the same amount of time to read each of the first 3 books. She took 56 min longer to read the fourth book than each of the first 3 books. She finished reading all the books at 16 40. What time did she start reading the fourth book?
Duration that Linda took to read the first book = 1 u
Duration that Linda took to read the second book = 1 u
Duration that Linda took to read the third book = 1 u
Duration that Linda took to read the fourth book = 1 u + 56 min

Total duration that Linda took to read the four books 
= 1 u + 1 u + 1 u + 1 u + 56 min
= 4 u + 56 min

4 u + 56 min = 2 h
4 u = 120 min - 56 min
4 u = 64 min  

1 u = 64 min ÷ 4 = 16 min

Duration that Linda took to read the fourth book
= 16 min + 56 min
= 72 min
= 1 h 12 min

1 h 12 min before 16 40: 15 28

Time that Linda started to read the fourth book = 15 28

Answer(s): 15 28