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In algebra, an equivalent expression is one that represents the same quantity even if it looks different. To find an equivalent expression, we often use mathematical properties such as the commutative law. For instance, in the given exercise, we start with the expression \((7x) y\). By applying the commutative law of multiplication, which states that \[a \cdot b = b \cdot a\], we can rearrange the multiplication to get the equivalent expression \[y (7x)\]. This shows that the order of multiplication doesn't affect the final product, making both expressions equivalent.

Multiplication properties in algebra help us manipulate and understand mathematical expressions better. Here are some important properties to remember:

1. **Commutative Property**: This property states that the order in which two numbers are multiplied does not change the result. For example, \[a \cdot b = b \cdot a\]. In our exercise, this property lets us rearrange \((7x) y\) as \[y (7x)\].

2. **Associative Property**: It states that the way in which numbers are grouped does not change their product. For example, \[a (b \cdot c) = (a \cdot b) c\].

3. **Distributive Property**: This property states that multiplying a number by a sum is the same as doing each multiplication separately. For instance, \[a (b + c) = ab + ac\].
These properties are tools that help us simplify and solve algebraic expressions efficiently.

Algebraic simplification is the process of rewriting an expression in a simpler or more efficient form. Simplifying algebraic expressions often involves using properties like the commutative, associative, and distributive laws.

For the given exercise, the expression \((7x) y\) can be simplified using the commutative law of multiplication. This gives us \[y (7x)\], which is already in a simple form. Simplification might also involve combining like terms, factoring, and reducing expressions.

Tips for simplification:
1. **Combine like terms**: If there are terms that have the same variables raised to the same power, you can combine them.
2. **Use properties**: Apply multiplication and addition properties to rearrange and simplify.
3. **Factor where possible**: Look for common factors that can make the expression easier to handle.

Through simplification, we make expressions easier to work with, whether we're solving equations, analyzing functions, or graphing relations.