The marked price of a pen is $\text{Rs. }200$ and a customer buys it for $\text{Rs. }153$ after two successive discounts. If the first discount is $10\%$, then the second discount is:

Given:
* Marked Price ($\text{MP}$) = $\text{Rs. }200$
* First discount = $10\%$

Price after the first discount:

$${\text{Price}}_1=200\times \left(1-\frac{10}{100}\right)=200\times 0.9=\text{Rs. }180$$

Let the second discount percentage be $d\%$. The final selling price is $\text{Rs. }153$:

$$180\times \left(1-\frac{d}{100}\right)=153$$

$$1-\frac{d}{100}=\frac{153}{180}$$

Simplifying the fraction by dividing the numerator and denominator by $9$:

$$1-\frac{d}{100}=\frac{17}{20}$$

$$\frac{d}{100}=1-\frac{17}{20}=\frac{3}{20}$$

$$d=\frac{3}{20}\times 100=15\%$$

The second discount is $15\%$.