1. **State the problem:** Simplify the fraction $\frac{11}{15}$ if possible. 2. **Formula and rules:** To simplify a fraction, divide the numerator and denominator by their greatest common divisor (GCD). 3. **Find the GCD:** The factors of 11 are 1 and 11. The factors of 15 are 1, 3, 5, and 15. The only common factor is 1. 4. **Simplify the fraction:** Since the GCD is 1, the fraction $\frac{11}{15}$ is already in simplest form. 5. **Final answer:** $\frac{11}{15}$ cannot be simplified further.