I went to the jewlery store and bought my friend a four hundred pesos ring. In my opinion, that is very expensive. She will be very happy for her birthday tommorow.

Tengo ir la joyeria y compré a mi amigo un anillo de cuatrocientos Pesos. En mi opinión, eso es muy costoso. Ella será muy feliz para su cumpleaños mañana.

Is this correct? also I don't know if I should say dollars or pesos or if I only need to say cuatrocientos.

Thank you for using the Jiskha Homework Help Forum and for trying the translation first! Happy to help you.

I went is the verb ir in the Preterit = Fui. The verb ir always takes the preposition "a" when followed by "to where" someone goes. Because you bought something FOR your friend, it will be the indirect object pronoun, both in front of the verb and then with the "a" you used. It is not necessary to capitalize "Pesos." The use of "eso" is perfect when referring to the entire situation (neuter) rather than to "the ring" which is masculine singular (ése). With "for" her birthday you have a choice of "para" meaning "in order for" or "por" = because of. In this case, "por" is better. As for dollars or pessos that is entirely your choice, but if you use pesos you won't have to worry about conversion from pesos to dollars. Put it all together and you should end up with:

Fui a la joyería y le compré a mi amigo un anillo de cuatrocientos pesos. En mi opinión, eso es muy costoso. (You had that one perfectly! Good job!) Ella será muy feliz por su cumpleaños mañana.

Please feel free to ask about anything that is not absolutely clear to you.

P.S. When you use "tengo que ir" it would mean "I have to go."

Sra

Your sentence is almost correct, but there are a few corrections needed. Here is the corrected version:

"Fui a la joyería y compré a mi amiga un anillo por cuatrocientos pesos. En mi opinión, eso es muy caro. Ella estará muy feliz por su cumpleaños mañana."

You should use "por" instead of "de" when indicating the price of something. Additionally, it is better to use "caro" instead of "costoso" to mean expensive. Finally, it is not necessary to specify the currency if you have already mentioned it once (in this case, pesos).

So, the correct sentence would be: "Fui a la joyería y compré a mi amiga un anillo por cuatrocientos pesos. En mi opinión, eso es muy caro. Ella estará muy feliz por su cumpleaños mañana."

Your sentence is almost correct! To clarify, if you want to specify the currency, you should mention either "pesos" or "dollars" after the amount. So, your sentence can be corrected as follows:

"Fui a la joyería y compré a mi amigo un anillo por cuatrocientos pesos/dólares. En mi opinión, eso es muy costoso. Ella estará muy feliz por su cumpleaños mañana."

Here, you have the option to choose either "pesos" or "dólares" to mention the currency in which you made the purchase. Also, keep in mind that "por" (meaning "for") is used before the amount to indicate the price of something.