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. Thank 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) = 30Each 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) = 100The system of linear equations is:          L +   B =  30       4L + 2B = 100 .