The correct option is B ₹840
Let the marked price of the dress be ₹x.
After a 25% discount, the price of the dress = (x−25x100).
According to the give data,
⇒(x−25x100)=630⇒ 100x−25x100=630⇒ 75x100=630⇒ 3x4=630⇒ x=630×43⇒ x=210×4⇒ x=840
∴The marked price of the dress is ₹840.