In a sale normal prices are reduced by 15% the sale price for CD player is £102 work out the normal price of the CD player

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