Learn French: Est-ce que votre équipe est prête ?

In French, the possessive adjective changes based on what is owned, not just who owns it. Even if you are asking multiple people, they only share one team (équipe). Because équipe is singular, you use votre. If they had multiple teams, it would be vos équipes.

I know that "équipe" is feminine. Why don't we use a feminine form of "votre"?

Unlike mon/ma and ton/ta, the possessive adjectives for plural owners (notre, votre, leur) do not change for gender. They only change for singular or plural. Because there is only one team, you use votre whether the noun is masculine or feminine.

Why is there an "e" at the end of "prête"?

Adjectives must match the gender of the noun they describe. The word for team, équipe, is feminine. Therefore, the adjective for "ready" takes its feminine form, prête, instead of the masculine form prêt.

Can I just ask "Votre équipe est prête ?" without using "Est-ce que" at the beginning?

Yes, you can! In spoken French, you can just state Votre équipe est prête and make your voice go up at the end. However, adding Est-ce que at the beginning is the standard and most common way to ask a yes-or-no question.