Answer: Either A or B
Step-by-step explanation:
Both A and B are the same answers, but the main answer should be
c+d=17, 4c+2d =54
C represents the number of cows and D represents the number ducks. The two and fours in front of the variables represents the number of legs the repesctive animal has.
c+d would mean how many animals are in the barn. Feel free to clarify the two same answers