Answer:
30% profit
Step-by-step explanation:
The amount by which the shopkeeper reduced the advertised selling price = 20%
The resulting profit over the cost price = 4%
Let x represent the initial advertised selling price, and let y represent the new selling price, and let c represent the cost price, we have;
x - 20% of x = y
x - x × 20/100 = y
0.8·x = y
y = c + 4% of c = 1.04·c
∴ 0.8·x = 1.04·c
x = 1.04·c/0.8 = 1.3·c
x = 1.3·c = c + 0.3·c = c + 30% of c
x = c + 30% of c
From which we have that the initial advertised selling price, x = The cost price + 30% of the  cost price
Therefore, the initial advertised selling price = The cost price + 30%profit on  cost price.
The shopkeeper would have made 30% profit if the dress had then been sold at the original selling price.
