An article is listed at Rs. 920. A customer pays Rs. 742.90 for it after getting two successive discounts. If the rate of first discount is 15%, the rate of 2nd discount is:

MP = 920
After first discount Marked Price (MP) become,
= 920 - 15% of 920 = 782
The Selling Price (SP) = 742.90
Let second discount was x% on 782
782 - x% of 782 = 742.90
$$\frac{{782x}}{{100}}$$ = 39.1
782x = 3910
x = 5%
Second Discount = 5%

Short-Cut
920 == 15%(1^st discount)) == 782 == x%↓(2^nd discount) ⇒ 742.90
Then,
$$\eqalign{ & x\% = \frac{{\left( {782 - 742.90} \right) \times 100}}{{742.90}} \cr & \,\,\,\,\,\,\,\,\,\,\, = \frac{{39.1 \times 100}}{{742.90}} \cr & \,\,\,\,\,\,\,\,\,\,\, = 5\% \cr} $$