By buying the necklace, she lost $300.
This means she has -300 dollars.
Then, she gained $600 for selling the necklace. Add 600.
-300 + 600 = 300
She now has $300 again.
Next, she buys it for $700. Subtract 700.
300 - 700 = -400
She has negative $400.
Finally, she sells it for $900. Add 900.
-400 + 900 = 500
She has $500 at the end.
Answer:
She gained $500 from the transactions.
