Answer:
The person at the horse race counts 74 heads and 196 legs that included an unknown number of horses and humans.
Let the number of horses that he counted be H and let the number of humans be M.
As both humans and horses have one head,
H + M = 74 ...(1)
Humans have 2 legs and horses have 4 legs, this gives
4*H + 2*M = 196 ...(2)
2*(1) - (2)
=> 4H + 2M - 2H - 2M = 196 - 148
=> 2H = 48
=> H = 24
M = 50
The person counts 24 horses and 50 humans