Verified answer

5.40

Original price * (percent discount) = amount saved

original price - saved = sale price

OR

original price - Original price * (percent discount) = sale price

or

Original price(1-discount %) = sale price

x(.9) = 4.86

divide both sides by .9

£5.40

£5.35

4.86 x 1.10 (the 1. bit is the current amount, the .10 bit adds on 10% of that amount)

round it up and it comes to 5.35

N * 0.90 = 4.86............(100% - 10% = 90% and 90/100 = 0.90)

4.86/0.90 = 5.40