The cost price of an article is 80% of its marked price for sale. How much per cent does the tradesman gain after allowing a discount of 12%?

Answer: Option C

Let the marked price = Rs. 100
Then the cost price = 80% of 100 = Rs. 80
After allowing 12% discount on MP,
SP become = Rs. 88.
% profit = $$\frac{8\times 100}{80}$$  = 10%