Solution:
we are given that
Each cow has 4 legs and each chicken has 2 legs.
A boy counts 42 heads and 144 feet.
we have been asked to find how many cows are there?
Let there are x cows and y chicken.
Then we can write
[tex] x+y=42....(i)\\
\\
\text{Sum of Heads}\\
\\
4x+2y=144\\
\\
\text{Sum of feet }\\
\\
\Rightarrow 2x+y=72....(ii)\\
\\
\text{Now solve these two equation together we get}\\
\\
2x+(42-x)=72\\
\\
2x+42-x=72\\
\\
x=72-42=30\\ [/tex]
Hence Number of cows=30
