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Addition is a fundamental operation in algebra. It involves combining numbers or algebraic terms to form a sum. When dealing with algebraic expressions, addition works similarly to numerical addition, but sometimes involves combining like terms. For instance, in expressions such as \( x + y + z \), each variable represents a number, and you simply add these numbers together once their values are known. Use the commutative property to reorder terms if necessary, as the order of addition does not change the sum.
It's also important to pay attention to the signs each term carries, as adding negative numbers follows different rules than adding positive ones.
To practice addition in algebra, work with varied expressions to see how different terms interact with each other.

Substitution is a powerful tool in algebra. It involves replacing variables in an expression with given numerical values to simplify the evaluation process. This method is essential when you're tasked with finding the numerical value of an algebraic expression for given variable values.
In the exercise, the substitution was performed by replacing \( x \), \( y \), and \( z \) with 3.6, 5, and 0.21 respectively, turning the expression \( x + y + z \) into \( 3.6 + 5 + 0.21 \).

• Identify the variables and their corresponding values.
• Replace each variable in the expression with its value.
• Ensure all number placements are correct to avoid mistakes.

After substitution, you're ready to proceed with arithmetic operations.

Arithmetic operations are the building blocks of mathematics. The most basic operations include addition, subtraction, multiplication, and division. Each operation follows specific rules and properties that make calculations straightforward and logical.
Addition is the process of combining two or more numbers. For the expression \( 3.6 + 5 + 0.21 \), you add these values in a step-by-step manner to arrive at a solution.

• First, add the first two numbers: \( 3.6 + 5 \), yielding \( 8.6 \).
• Next, add the result to the third number: \( 8.6 + 0.21 \), arriving at \( 8.81 \).

In arithmetic, it is beneficial to perform operations in a sequence that simplifies the process and helps prevent errors. Practicing basic operations with different number types, such as decimals, whole numbers, and fractions, will enhance your mathematical ability.