Marked price = ₹1800
First discount = 18%
Discount amount:
1800×10018=324
Price after first discount:
1800 − 324 = ₹1476
Let the additional discount be (x%).
Then:
1476(1−100x)=1220
1−100x=14761220
100x=1−14761220=1476256
x=1476256×100≈17.34
Additional discount = 17.34%