Calculate Total Discount

The total discount given on the article is the difference between the Marked Price and the Selling Price: $1320 - 330 = 990$.

$\text{Total}\ \text{Discount} = 990$

Equate Nominal Values

Since two equal discounts of value $X$ were given, each discount must be half of the total: $X = 990 / 2 = 495$.

$X = 495$

Find the percentage d

The first discount is $d\%$ of the Marked Price, which equals the first discount amount ($X$): $\frac{d}{100} \times 1320 = 495$.

$d = \frac{495}{1320} \times 100$

Solve for d

Dividing 495 by 1320: $495 / 1320 = 0.375$. Converting to percentage: $0.375 \times 100 = 37.5$.

$d = 37.5$