Hi,
So the refrigerator is £780 at the 40% off sale therefore it is only 60% of the original price which was 100%.
So we do £780 / 60 = 13 which is 1% of the original price so to get the total amount we multiply this by 100 to get 1300 which is the full 100%.
Therefore the original price before the sale was £1300.
Hope this helps !