In a pet shop there are 120 eyes and 172 legs. How many birds are included in these? Choose the correct answer:
A) 33
B) 34
C) 35
D) 36
E) 37
Let there are x birds and y puppies.   Each bird and puppy has 2 eyes. Each bird has 2 legs and each puppy has 4 legs.   Then 2x+2y = 120 =&gt; x+y = 60 (i)   2x+4y = 172 =&gt; x+2y = 86 (ii)   Solving (i) and (ii) we get   y = 26 &amp; x = 34   So birds are 34   ANSWER:34
<result>B</result>
In a pet shop there are 120 eyes and 172 legs. How many birds are included in these?