Final answer:
The artist must sell more than 18 necklaces to make a profit.
Step-by-step explanation:
To find the number of necklaces the artist must sell to make a profit, we need to solve the inequality 12n > 135 + 4.50n, where n represents the number of necklaces sold.
First, we can simplify the inequality by subtracting 4.50n from both sides: 12n - 4.50n > 135.
This simplifies to 7.50n > 135.
Finally, we divide both sides of the inequality by 7.50 to solve for n: n > 18.
Therefore, the artist must sell more than 18 necklaces to make a profit.