To solve the problem, follow these steps:

Step 1: Calculate the total number of students

There are 12 boys and 13 girls.
Total students = 12 + 13 = 25.

Step 2: Determine the number of favorable outcomes

The favorable outcome is selecting a boy, so there are 12 favorable outcomes.

Step 3: Compute the probability

Probability = (Number of favorable outcomes) / (Total number of outcomes)
Probability = 12/25 = 0.48

Answer: 12/25 (or 0.48)
$\boxed{\dfrac{12}{25}}$

作者声明:本文包含人工智能生成内容。