Mollie B. answered 01/28/20
High School & College Tutor for Varied Subjects
Use the following facts to build two equations: 29 heads = 29 animals, goats have 4 feet, and ducks have two feet.
29 = G + D (where G = goats and D = ducks)
82 = 4G + 2D (where 4 and 2 represent the number of feet of goats and ducks respectively)
Rearrange first equation in order to substitute for one variable in the second equation:
29 = G + D --> G = 29 - D
82 = 4(29 - D) + 2D
Distribute and simplify:
82 = 116 - 4D + 2D
82 = 116 - 2D
2D = 34
D = 17
Now substitute the D value into the rearranged first equation:
G = 29 - 17
G = 12
There are 17 ducks and 12 goats.