Percentage Discount Total

Hi All,

Can anyone help me with the following.

I have the formula =SUM(D2*(20/100)) which gives me the discount value of cell D2 i.e if D2 = £10 then the SUM = £2

But I want the formula to work out the total minus the sum ie.

£10 - 20% = £8

I hope ive made this clear, maybe im just going about it the wrong way.