Here's why:
* "Salida" means "exit" or "departure" in Spanish. It's a feminine noun.
* "Un" is the masculine singular indefinite article, used before masculine nouns.
Since "salida" is feminine, you need to use the feminine indefinite article "una".
Possible correct phrases:
* "Una salida" - This means "an exit" or "a departure".
* "La salida" - This means "the exit" or "the departure".
It's important to use the correct gender and articles in Spanish to ensure your sentences are grammatically correct.