Answer:
51
Explanation:
The expression to be evaluated is x² - 3yz, where x = 9, y = -5, and z = -2.
To evaluate this expression, we substitute the given values of x, y, and z into the expression and perform the necessary calculations.
Substituting the values into our given expression:
⇒ x² - 3yz
⇒ (9)² - 3(-5)(-2)
Now calculating:
⇒ (9)² - 3(-5)(-2)
⇒ 81 - 30
∴ 51
Therefore, when x = 9, y = -5, and z = -2, the expression x² - 3yz evaluates to 51.

Additional Terminology/Concepts:
Expression: A mathematical statement that contains variables, numbers, and operations but doesn't have an equal sign.
Evaluate: To find the numerical value of an expression for specific given values of the variables.
Substitution: The process of replacing variables in an expression with their given values.
Calculation: The act of performing mathematical operations to determine a result.