there ar 7 of each animal
1=6(2 legs from the duck, 4 legs from the pig)
2=12(4 legs from the ducks, 8 legs from the pigs)
3=18(6 legs from the ducks, 12 legs from the pigs)
4=24(8 legs from the ducks, 16 legs from the pigs)
5=30(10 legs from the ducks, 20 legs from the pigs)
6=36(12 legs from the ducks, 24 legs from the pigs)
7=42(14 legs from the ducks, 28 legs from the pigs)
