"Vous voulez une vache."
Translation:You want a cow.
I learned another use for "vache" in French. The phrase "oh, la vache!" is basically the equivalent of "oh, my God!" or "oh, geez!" Children from France visited my school and said it quite often. Particularly while playing soccer, lol. We asked why they kept saying "oh, the cow" and they laughed and explained it to us. The literal translation was so bizarre to me that I never forgot it. I say the phrase quite often myself, now.
So I translated it as "Y'all want a cow," considering that voulez was plural. I have used "y'all" as a translation of "vous" before and it has counted it right. So why did it say I was wrong? I know sometimes vous is just formal you, singular, but how could I know that? also, this seems like a pretty informal sentence.
There is a difference. "Want" is present indicative, and "would like" is conditional. The conditional is usually used in "if X, then Y" kinds of constructions, but it's often used on its own to sweeten a request. If, for example, you're at a restaurant and you want to ask the waiter to bring you something, it's more polite to use the conditional, "Je voudrais ..." rather than the indicative "Je veux ..." The full indicative conjugation of vouloir: veux, veux, veut, voulons, voulez, veulent. The conditional: voudrais, voudrais, voudrait, voulions, vouliez, voudraient. Here's a good article about the use of the conditional in French: http://www.fluentu.com/french/blog/french-conditional-tense/