Let's answer this step-by-step.
First of all, let's estsblish the original price of the commodity as being 100%. Therefore:
Original price of commodity = 100%
Then, when A sold the commodity to B, it was sold at a 10% profit. Therefore:
Price of commidity when A sold to B:
100% x 1.1 = 110%
After that, when B sold it back to A, it was sold at a 10% loss. Therefore:
Price of commodity when B sold to A:
110% x 0.9 = 99%
Hence, A now has 99% of the original value of the commidity.
