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Both is possible. "voastră" is formal and "ta" is informal.

The general rule is that the adjective (the possessive adjective in this case) has to agree in gender and number with the noun it determines.

• tău - singular masculine / neuter
• ta - singular feminine
• tăi - plural masculine
• tale - plural feminine

Examples:

• masculine: un băiat - doi băieți, băiatul tău - băieții tăi
• feminine: o fată - două fete, fata ta - fetele tale
• neuter: un măr - două mere, mărul tău - merele tale

There's no difference in meaning between este and e.