There are only horses and ducks on a farm. There are 80 animals in all and the number of ducks is ca

There are only horses and ducks on a farm. There are 80 animals in all and the number of ducks is called n. How many horse legs are there on the farm?

Number of duck legs = 2 legs * n ducks = 2n legs

Number of horses = 80 - n
Legs per horse = 4
Total horse legs = 4(80 - n) = 320 - 4n