12. Farmer Fatima rears chickens and goats. Today she returned from market and said, "I sold 80 animals, and now there are 200 fewer legs on my farm than before!"
How many goats did she sell?
A 15
B 20
C 25
D 30
E 35
12. B Let the number of chickens and goats sold be $c$ and $g$ respectively.
Then, since 80 animals are sold, we have $c+g=80$.
Also, $2 c+4 g=200$, since the chickens have two legs and the goats have four legs.
Dividing the second equation by 2 , we obtain $c+2 g=100$.
Then, subtracting the first equation gives $g=100-80=20$.
So 20 goats were sold.