My wife had a previous marriage

Good day Atty.

I was married to a girl, who left me 6 months after I went abroad. She had another man, and right now they are living together and has kids already.
After a few years, I came back to the Philippines. I took my Cenomar and also hers and found out that she has a previous marriage with another man which appeared in her Cenomar, however it seems that she was only 17 at the time of their marriage.

My Questions:
1.) Is her first marriage valid?
2.) Is our marriage valid?
3.) Under what grounds can I file for annulment of our marriage? And how can I file for an annulment?
4.) How much will be the total cost of the annulment?
5.) How long will the process take for this case?

Thanx,

so are you sure that she was 17? what year was your wedding?

if she had a previous marriage, then yours is not valid, but you have to file a a petition for declaration of nullity on the basis of bigamy.

cost depends on which lawyer you retain.