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

• A. Expression
• B. Equation
• C. Both A and B
• D. None of the above

Answer: (B)

Verified step by step guidance

1. Understand the difference between an expression and an equation: An expression is a mathematical phrase that contains numbers, variables, and operations but does not have an equals sign. An equation is a mathematical statement that shows two expressions are equal, and it always contains an equals sign (\(=\)).
2. Look at the given problem: \$4\left(a - 2\right) = 21$. Notice that it contains an equals sign, which means it is stating that one quantity is equal to another.
3. Since the problem has an equals sign, it is not just an expression; it is an equation.
4. Therefore, identify \$4\left(a - 2\right) = 21$ as an equation because it shows equality between two expressions.
5. Remember, if there was no equals sign, for example \$4\left(a - 2\right) + 21$, that would be an expression instead.