i have 100.00 to spend on 100 animals. the chickens are .05 each, the pigs are 5.00 each, and the cows are 10.00 each.

What is your question?

Can I spend less than $100 ?
Can I have less than 100 animals ?

let the number of chickens be x
let the number of pigs be y
then the number of cows is 100-x-y

so ...
.05x + 5y + 10(100-x-y) = 100
times everything by 20
x + 100y + 200(100-x-y) = 2000
x + 100y + 20000-200x - 200y = 2000
-100y - 199x = -18000
100y = -199x + 18000
y = (-199/100)x + 180

If you MUST spend $100 and you MUST have 100 animals there is obviously no solution.

If the condition is as I stated at the top of my reply, there are quite a few cases that will work, as long as the number of animals does not exceed 100 and the cost does not exceed $100
e.g. 2 cows, 10 pigs and 10 chicken satisfy that condition.

BTW, 5 ¢ for a chicken ?????
When was your mathbook printed, in 1850?