Unfortunately, you cannot replace your Physical Education (P.E.) marks with your Chemistry marks in the CBSE 2024-25 board exams.

CBSE has specific rules regarding the calculation of the overall percentage. Generally, the marks of all subjects are included in the calculation, and there isn't an option to replace a lower-scoring subject with a higher-scoring one.

However, if you're concerned about your Chemistry performance, here are a few strategies you can consider:

• Seek help: Reach out to your teacher or a tutor for extra assistance.
• Practice regularly: Solve as many practice questions as possible.
• Focus on weak areas: Identify the topics you find challenging and spend extra time on them.
• Time management: Practice time management during your exams to ensure you can answer all questions.

Remember, while it's important to strive for high grades, a single subject shouldn't define your overall performance. Focus on understanding the concepts and doing your best in all subjects.