I never saw this until today, but it seems to have been going the rounds for some years and generated a lot of discussion. Googling the first phrase gets over 2 million hits.
A man buys a horse for £60 and sells it for £70. He then repurchases for £80, and sells it for £90.
Has he gained or lost, if so by how much? Or has he broken even?
Sometimes it’s a goat or a pig etc.