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Undoing Division

Part of the Fundamentals section of Coddy's Algebra journey. Lesson 6 of 61.

$\frac{x}{4} = 18$

$\frac{x}{4}$ means $x$ divided by 4. Multiplying is the opposite of dividing, so multiply both sides by 4:

$\frac{x}{4}\cdot 4 = 18\cdot 4$

$x = 72$

Check: $\frac{72}{4} = 18$ . Multiplying undoes dividing. For example, four friends share a bill and each pays $18. The bill was $72.

Challenge

Find $x$ . Pick what to do to both sides, then work out each side. Done means $x$ is alone on one side and a number is on the other.

Try it yourself

\frac{x}{6} = 14

Get $x$ alone

All lessons in Fundamentals

1What an Equation Is

The Equation The Same to Both Sides Undoing Subtraction Recap: First Equations

4Two-Step Equations

Two Layers to Undo Subtract, Then Divide Add, Then Divide A Division Inside Negatives in Two Steps Recap: Two-Step Equations

7Fractions in Equations

A Fraction Coefficient Clearing One Denominator Two Denominators A Fraction Around a Sum Cross-Multiplying Recap: Fractions

10From Words to Equations

Phrases into Expressions Sentences into Equations Consecutive Numbers Age and Money A Perimeter Problem Recap: Words

2One-Step Equations

Undoing MultiplicationUndoing DivisionInverse Operations Recap: Two Moves in a Row

5Tidying First

Like Terms Terms and Numbers Mixed The Distributive Property Distributing a Subtraction Tidy, Then Solve Recap: Tidying First

8Decimals and Percent

Decimal Coefficients Two-Step with Decimals Adding a Percent Percent Equations Recap: Decimals

11Formulas

Using a Formula Finding a Missing Value Solving for a Letter Temperature Recap: Formulas

3Negative Numbers

Below Zero A Negative Answer Negative Coefficients The Opposite of x Recap: Negatives

6Variables on Both Sides

x on Both Sides Gathering the x's Numbers and x's Everywhere Parentheses on One Side When x Is Negative Recap: Both Sides

9Special Cases

No Solution Always True Checking a Solution Recap: Special Cases

12Final Challenges

Parentheses on Both Sides Fractions and x's Decimals on Both Sides The Story Problem