1. **Problem:** Evaluate the numerical expression $3 \times (4 + 5) - 6$. 2. **Formula and rules:** Use the order of operations (PEMDAS): Parentheses, Exponents, Multiplication and Division (left to right), Addition and Subtraction (left to right). 3. **Step-by-step solution:** 1. Calculate inside the parentheses: $4 + 5 = 9$ 2. Multiply: $3 \times 9 = 27$ 3. Subtract: $27 - 6 = 21$ 4. **Answer:** The value of the expression is $21$.