Answer:
47 Ducks and 7 piglets.
Explanation:
Lets try 27 of each to start
Ducks Piglets Total legs
27 27 54 + 108 = 162. Too many
30 24 60 + 96 = 156 Too many. Increase the ducks by 10:
40 14 80 + 56 = 136.
50 4 100 + 16 = 116 This < 122 so ducks between 40 and 50..
45 9 90 + 36 = 126 Too high so increase ducks:
46 8 92 + 32 = 124 Close.
47 7 94 + 28 = 122.