Answer: She will pay $ 720 for the computer.
Step-by-step explanation:
Since, the cost price of the laptop = $ 900,
Also, after getting the $ 100 gift card,
The new price of the laptop = $ 900 - $ 100 = $ 800
According to the question,
The store is offering 10% off on all computers.
The final price of the laptop = 800 - 10% of 800
= 800 - 80
= $ 720,
Hence, $ 720 will be paid for the laptop.