Hello,

Just remeber it algerbraically, where x is the original price (£)

34 / x = 0.85 (1 - 0.15 or 15%)

=> 34 = 0.85x

=> x = 34 / 0.85

=> x = 40

Just remember:

Minus the new% value from 100% (100% - 15%), make it a decimal (1 - 0.15 = 0.85) Then divide your NEW price by the decimal. (34 / 0.85)

Simple

the answer is £40