A farmer and his wife go to the market to exchange their poultry for cattle knowing that eighty-five chickens equals one horse and one cow. It is also known that five horses have the same value as twelve cows.

*"John"*said the wife, *"Let's take as many horses as we have already bought, so we will only have seventeen horses and cows to feed during the winter"*.

*"I think we should have more cows than those"*, replied her husband.*"What's more, I think if we double the number of cows we have bought we would have a total of nineteen cows and horses and we would have the exact amount of chickens to make the exchange"*.

These simple country people knew nothing about algebra and yet they knew exactly how many chickens they had and how many horses and cows they could get for them.

We ask our fans to determine from the data provided **how many chickens the farmer and his wife brought to the market**.

#### Solution

It is evident to any farmer that a cow costs 25 chickens and that a horse is worth 60.

They must have already bought 5 horses and 7 cows that are equivalent to 475 chickens and since they have enough to get 7 more cows, they have 175 chickens left, which gives us a total of 650.