Fred Says

Fred is very confused! He's been looking at some trainers that are on sale.
Before the sale they cost £25.
The shop says there is a sale on all footwear today.
BUT on the red price label of the pair he likes, it says there is an extra saving of 5% on all trainers with a red label.

Fred thinks these are a good buy!
BUT...how does he work out how much they are going to cost him?

Does he:

take off 10% first, then 5% after that?
take off 5% first then 10% after that?
take off 15% straight away?

Does it make any difference? How do you know?
What would you tell Fred to tell the shop assistant?

What if...the trainers were £50, £100?

Sometimes shop bills show VAT, a tax paid to the government, seperately.
What if .. the trainers were reduced by 10% but there was a tax of 5% added?
Would it matter which was calculated first, the VAT or the sale price?