Learn Spanish (Latin America): ¡El libro cuesta quince dólares y yo tengo cero! - The book costs fifteen dollars and I have zero!

The numbers 11 through 15 have their own special names in Spanish, just like in English. Instead of combining ten and five, you just use the single word quince.

Does the word cero change if I am talking about feminine nouns?

No! Unlike uno, which changes to match the gender of the noun (like un libro or una casa), cero never changes its ending. It is always cero.

Why is the verb cuesta instead of "costa"?

The dictionary form of the verb "to cost" is costar. It is a "stem-changing" verb. This means that when you use it for "it costs", the o in the middle splits into two vowels, becoming ue.

Why does dólares have an accent mark?

The singular word is dólar. To make it plural, you add -es because it ends in a consonant. The accent mark stays on the o in dólares so your voice still stresses the exact same syllable.

Why did they use yo tengo instead of just tengo?