Astore sign reads take 75% off the original price when you take an additional 15% off the sale price which is 60% off the regular price is the store signs accurate explain

I you take 75% off the original price, 25% remains.

If you take 60% off the original price, 40% remains. Taking 15% off that means you take off an additional 0.15*40% = 6% of the original price, so end up with
  40% -6% = 34%
of the original price. This is considerably more than 25% of the original price.

The store sign is not accurate, because the "additional 15%" is of the sale price, not the original price.