Tourist: "how many birds and lions do you have in your zoo? " zookeeper: "there are 30 heads and 100 feet." find the number of each animal. i need to know how to set this problem up in a system of linear equations. you.

Each lion has 1 head.  The number of lion heads is L .
Each bird has 1 head.  The number of bird heads is B.
The total number of heads of all species is (L + B) = 30

Each lion has 4 feet.  The number of lion feet is 4L .
Each bird has 2 feet.  The number of bird feet is 2B .
The total number of feet of all species is (4L + 2B) = 100

The system of linear equations is:

         L +   B =  30
       4L + 2B = 100 .