Understanding the Problem
To solve for the gain or loss percentage when the article is sold at a 30% discount, we first need to establish the cost price (CP) and the selling price (SP) based on the initial conditions provided.

Given Data
- Discount = 13%
- Gain = 30.5%

Calculating the Selling Price at 13% Discount
- Let the cost price (CP) be \( x \).
- The selling price (SP) can be calculated using the gain formula:
\[
SP = CP + \text{Gain} = x + 0.305x = 1.305x
\]
- Since the article is sold at a 13% discount:
\[
SP = \text{Marked Price} - \text{Discount} = \text{Marked Price} - 0.13 \times \text{Marked Price} = 0.87 \times \text{Marked Price}
\]
- Equating the two SPs:
\[
1.305x = 0.87 \times \text{Marked Price}
\]

Finding the Marked Price
- Rearranging gives us:
\[
\text{Marked Price} = \frac{1.305x}{0.87} \approx 1.5x
\]

Calculating Selling Price at 30% Discount
- Now, if the article is sold at a 30% discount:
\[
SP = \text{Marked Price} - 0.30 \times \text{Marked Price} = 0.70 \times \text{Marked Price}
\]
- Substituting the Marked Price:
\[
SP = 0.70 \times 1.5x = 1.05x
\]

Calculating Gain/Loss Percentage
- Gain/Loss = \( SP - CP = 1.05x - x = 0.05x \)
- Gain/Loss Percentage =
\[
\left( \frac{0.05x}{x} \right) \times 100 = 5\%
\]

Conclusion
When sold at a 30% discount, the article results in a gain of **5%**.