Respuesta :

0000000
Cows (C)→ 4 legs
Chickens (c) → 2 legs
C+c=13    |×4
4C+2c=36

4C+4c=52
4C+2c=36
--------------- (-)
       2c=16
       c=8 chickens

C=13-8
C=5 cows