To determine which inequality describes the situation, we first note that Lin has a total of $50 on her gift card. She spends $9.99 on an album, leaving her with some remaining balance. Lin also wants to buy \(n\) songs, each costing $1.29.
The total cost of the album plus the songs can be represented as:
\[ 9.99 + 1.29n \]
Since Lin cannot exceed the amount on her gift card, this total cost must be less than or equal to $50. Therefore, the inequality that represents this situation is:
\[ 9.99 + 1.29n \leq 50 \]
So, the correct option is:
2. \(9.99 + 1.29n \leq 50\).