Answer:
The number of frame he need to sell in order to make a profit is:
6 frames.
Explanation:
Let he sells " n " frames in order that he earns profit.
As we know that he will earn profit when the total amount on selling n items exceeds the cost of supplies.
i.e. the selling price is more than the cost price .
( Since, Profit is calculated by the formula:
Profit= Selling price-Cost price )
Selling price of 1 frame=$ 8.50
Selling price of n frame= $ (8.50 n)
Hence, we need to find n such that:

Hence , we have:

Hence, n=6
He needs to sell 6 frames in order to make a profit.