Answer :

There could be lots of answers. I'm going with 5 goats and 7 ducks.
x=goats y=ducks 4x+2y=34 x+y=11 -y -y x=11-y 4(11-y)+2y=34 44-4y+2y=34 44-2y=34 -44 -44 -2y=10 /2 /2 y=5 x+y=11 x+5=11 -5 -5 x=6 goats=6 ducks=5