Identify the following as either an expression or equation.
$4(a-2)=21$

• A. Expression
• B. Equation

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the difference between an expression and an equation. An expression is a mathematical phrase that can contain numbers, variables, and operations but does not have an equals sign. An equation is a statement that two expressions are equal, and it always contains an equals sign (\(=\)).
2. Step 2: Look at the given mathematical statement: \$4\left(a - 2\right) = 21\(. Notice that it contains an equals sign (\)=$), which means it is stating that two quantities are equal.
3. Step 3: Since the statement has an equals sign, it is not just a phrase or a combination of terms; it is a complete statement that can be solved for the variable \(a\).
4. Step 4: Therefore, this mathematical statement is classified as an equation, not an expression.
5. Step 5: To summarize, any mathematical statement with an equals sign is an equation, while those without are expressions.