Answer:
n ≥ 5
Step-by-step explanation:
The money that Janie earns (E) must be greater than or equal to the cost (c) of the CD.
In symbols,
    E ≥ c
2n + 3 ≥ 13   Subtract 2 from each side
   2n ≥ 10    Divide each side by 2
    n ≥ 5
Janie must do five or more chores to buy the CD.