I am having a hard time

Question

A farmer notes that in a field full of cows and ducks there are 2929 heads and 8080 feet. How many of each animal are there?

Answer 1

d + c = 2929 heads

2d +4c = 8080 legs

multiply 1st equation by 2

then subtract from 2nd equation

2d +2c = 2(2929) = 5858

2c = 8080-5858 = 2222

c = 2222/2 = 1111 cows

d = 2929-1111 = 1818 ducks

2(1818) + 4(1111)

= 3636+4444

= 8080 legs