£50
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Let the original price be x.
We know that after 20% discount the price is £40.
Set us the following equation and solve for x:
- x - 20% of x = £40
- x - x*(20/100) = £40
- x - 0.2x = £40
- 0.8x = £40
- x = £40/0.8
- x = £50
So the initial price was £50.