I want to solve this problem by the shortcut method taught in my class. So it will be highly helpful if somebody knows this method and would resolve my doubt in the shortcut method I have used here.
Q.A shopkieeper sells an article at 12% discount on the marked price and makes a profit of 10%.If he gives a discount of 4% he will earn a profit of Rupees 40. Find the marked price of the article. Correct answer :Rs 250. Where might have I gone wrong?
My Attempt:
CP=Cost Price, SP=Selling Price, MP=Marked Price

I found your mistake.
96 - 80 = 16. Not 6.
Then you get correct result.