The cost price of a particular amount of articles is same as the number of articles. Selling price of the articles comes out to be 20. Over the whole transaction 25% is gained. What is X?

The problem seems to be missing some information. However, I'll try to interpret it as best as I can.

1. Let's denote the cost price of each article as 'c' and the number of articles as 'n'. According to the problem, c = n.

2. The selling price of the articles is given as 20. So, the total cost price of the articles is 20.

3. It's mentioned that there's a gain of 25% over the whole transaction. This means that the selling price is 125% of the cost price.

4. We can set up the equation as follows: 1.25 * cost price = selling price. Substituting the given values, we get 1.25 * c = 20.

5. Solving this equation will give us the value of 'c' (which is also 'n' as per the problem).

However, the problem mentions 'X' but does not specify what 'X' represents. If 'X' is supposed to represent the cost price or the number of articles, then we can solve the equation in step 4 to find 'X'. If 'X' represents something else, we would need more information to solve for 'X'.