First, we need to calculate the total cost of the iPhone and it is calculated as:

So, replacing the initial cost by $899 and the tax rate by 0.0825, we get:

It means that you need to save $973.1675 to buy your new iPhone.
Then, every week you save 15% of $565. This quantity is calculated as:

So, every week you save $84.75
Finally, to calculate the number of weeks that you need to buy the new iPhone we need to divide the total cost by the quantity saved per week as:

Therefore, the answer is 11.48 weeks
Answer: 11.48 weeks