Farmer John (not the bacon guy) raises ducks and cows. He has 54 animals which all together have 122 feet. How many of each type of animals does Farmer John have?

Answer 1

C + D = 54

therefore C = 54-D

4C + 2D = 122

Substitute 54-D for C in the third equation and solve for D. Insert that value into the second equation to solve for C. Check by putting both values into the third equation.