Explanation: To solve this problem, we need to set up an algebraic equation based on the given information. Let's denote the cost price of the trousers as \( T \) and the cost price of the shirt as \( S \).
According to the problem, the total cost price of the shirt and trousers is Rs 371. Therefore, we can write the equation:
\[ S + T = 371 \]
We are also given that the shirt costs 12% more than the trousers. This means:
\[ S = T + 0.12T \]
\[ S = 1.12T \]
Now, we substitute \( S = 1.12T \) into the first equation:
\[ 1.12T + T = 371 \]
\[ 2.12T = 371 \]
To find the cost price of the trousers, we solve for \( T \):
\[ T = \frac{371}{2.12} \]
\[ T = 175 \]
Thus, the cost price of the trousers is Rs 175.
To verify, we calculate the cost of the shirt:
\[ S = 1.12 \times 175 = 196 \]
Adding the cost of the shirt and trousers:
\[ 175 + 196 = 371 \]
This confirms that the cost price of the trousers is indeed Rs 175, and the correct answer is (B) 175.
This problem demonstrates the application of algebraic equations and percentage calculations to solve real-world problems involving cost prices. It is important to set up the equations correctly and solve them step-by-step to ensure accuracy.