Monthly income = ₹90000
Income tax = 20100×90000 = ₹18000 (1 mark)
Remaining amount = ₹90000 - ₹18000 = ₹72000 (1 mark)
75% of the remaining = 75100×72000 = ₹54000 (2 marks)
∴ The total amount left with him at the end of the month = ₹72000 - ₹54000 = ₹18000