The price of an article was cut 20% for a sale. by what percent must the item be increased to again sell the article at the original price?

In order to achieve its original price, the item's price must be increased for: 25%

Let's assume that x = original price (100 %)

after the first cut,

x - 0.2 = 0.8x

now, we need to return it into x, technically we need to add it with 0.2 x again, but since the percentage now is taken from 0.8x, the calculation will be:

0.2x / 0.8x = 1/4 = 0.25 = 25%