I have $100 to buy 100 animals. 1 cow costs $5, 1 sheep costs $1 and 1 pig costs 5 cents?

Do you have a question then?

There are two solutons to this, where you spend precisely $100 to buy precisley 100 animals. One of the answers is immediately obvious; the other less so.

Its an algebra question, its 20 years since I done algebra. The question is already there, a hundred dollars to buy a hundred animals and the prices are there, and you have to have 1 of each.

There are two solutons to this, where you spend precisely $100 to buy precisley 100 animals. One of the answers is immediately obvious; the other less so.
Yes , you need to use all the money and buy at least one of each animal.. I just forget how to use algebra

You don't really need algebra, just logic. It's not that complicated. Think about this - if you buy any pigs at all you must buy then in multiples of 20, or else you can't get the total spend to be in whole dollars. And then the number of sheep you buy added to what you spent on pigs must come to a multiple of 5. So my suggestion is to see what happens if you buy 0 pigs, then try 20 pigs, Then 40, etc.up to 100. Like I said before - there are two solutions to this puzzle.