Ok, so the discount is given in a percentage, in this case 15%. The
sale price is going to reflect 15% of the original price minus the
discount, so...
Sale £ = original£ - original£ x .15
If we use some algebra, we can reorganize the equation to solve for the original price...
Sale $ = original$ - original $ x .15
Sale $ = original$ (1 - .15)
Sale $ = original$ x .85
original$ = sale$/.85
So now we can plug in our values
original price = 102/.85
original price = £120
