Lê Quốc Trần Anh Coordinator
28/03/2018 at 09:27-
Fixida 28/03/2018 at 11:16
A group of kangaroos of four colors.
Lê Quốc Trần Anh selected this answer.
Then the 29th kangaroo is colored:
29: 4 = 7 (residual 1)
Then the 29th kangaroo is black.