Big Ideas Math: Modeling Real Life, Grade 6
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Exercise 18 Page 276

Use the Multiplication Property of Equality to eliminate the division.

k=63

Practice makes perfect
To solve the equation, we have to isolate k on one side. Using the Multiplication Property of Equality, we will multiply both sides of the equation by 3. This will eliminate the denominator of the fraction and isolate k.
k ÷ 3 = 21
k/3=21
k/3* 3=21* 3
k=21* 3
k=63
To check that this solution is correct, let's substitute k=63 into the original equation and simplify.
k ÷ 3 = 21
63÷ 3? = 21
21=21 ✓
Since the left-hand side and right-hand side are equal, k=63 is the correct solution.

Extra

Properties of Equality

There are four main Properties of Equality that we use when solving linear equations.

Properties of Equality
Addition Property of Equality If a=b, then a+c=b+c.
Subtraction Property of Equality If a=b, then a-c=b-c.
Multiplication Property of Equality If a=b, then ac=bc.
Division Property of Equality If a=b and c is not 0, then a/c=b/c.

In later chapters, you will learn about some more advanced Properties of Equality. As an example, there is a property for when we need to eliminate a radical or an exponent.

Power Property of Equality

If a=b, then a^m=b^m.