Cost price of 20 article= selling price of x articles
so if by selling x articles the profit is 25 %
Therefore, the price of each article if x articles are sold for 20 units will be 20/x
since profit is 25%
each article would be (1+25/100)×1
20/x = (1+25/100)×1
= 20/x = ( 100 + 25 /100) × 1
= 20/x = (125/100) × 1
cancel common factors
4/x =1/4
cross multiplication
4×4= 16
1× x = x
therefore x = 16
hope this helps you