c = number of chickens
d = number of ducks
c = 4d because there are 4 times as many chickens as ducks
c = d+72 because there are 72 more chickens
4d = d+72 after using substitution
4d-d = 72
3d = 72
d = 72/3
d = 24
c = 4d = 4*24 = 96 ...or... c = d+72 = 24+72 = 96
Answer: There are 96 chickens and 24 ducks