Explanation:

- Selling Price (SP) and Loss Analysis:

- Article sold for $640.

- Loss is 15% of selling price.

- Loss = 15% of $640 = $96.

- Hence, the Cost Price (CP) = Selling Price + Loss = $640 + $96 = $736.

- Target Selling Price for Gain:

- To gain 15% on cost price:

- Target Selling Price = Cost Price + 15% of Cost Price.

- Target = $736 + (15% of $736) = $736 + $110.40 = $846.40.

- Options:

1. 832

2. 846.40

3. 835

4. 836.60

The correct price to sell for a 15% gain is 846.40.

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