**Vocabulary**

proportional relationship

**TEKS** 8(1)(D), 8(4)(B), 8(5)(A)

**Example Graphing Proportional Relationships**

A video game store has a frequent shopper program. You earn 4 points for every video game you buy. Draw a graph to model this situation.

You need 48 points for a free game. How many video games do you need to buy to have enough points for a free game?

**Solution**

For every game you buy, you earn 4 points. Since you can only buy entire games, it only makes sense to plot points with *x*-coordinates that are whole numbers. For each point on the graph, the *y*-coordinate should be four times the *x*-coordinate.

Since you need 48 points for a free game, look for a point on the graph until you reach a *y*-coordinate of 48.

You need to buy 12 games to have enough points for a free game.

Digits, Grade 8, Volume 1, Homework Helper
Unit A: Number and Operations
Math Symbols
Formulas Measures
Properties

Topic 1: Rational and Irrational Numbers

Unit B: Proportionality
- 1-1: Exploring Irrational Numbers
- 1-1: TEKS Practice
- 1-2: Approximating Irrational Numbers
- 1-2: TEKS Practice
- 1-3: Comparing and Ordering Rational and Irrational Numbers
- 1-3: TEKS Practice
- 1-4: Exploring Scientific Notation
- 1-4: TEKS Practice
- 1-5: Using Scientific Notation to Describe Very Large Quantities
- 1-5: TEKS Practice
- 1-6: Additional Problem Solving
- 1-6: TEKS Practice

Topic 2: Proportional Relationships, Lines, and Linear Equations
Topic 3: Defining and Comparing Functions

Unit C: Expressions, Equations, and Relationships
- 2-1: Representing Proportional Relationships
- 2-1: TEKS Practice
- 2-2: Linear Equations: y = mx
- 2-2: TEKS Practice
- 2-3: The Slope of a Line
- 2-3: TEKS Practice
- 2-4: Unit Rates and Slope
- 2-4: TEKS Practice
- 2-5: The y-intercept of a Line
- 2-5: TEKS Practice
- 2-6: Linear Equations: y = mx + b
- 2-6: TEKS Practice
- 2-7: Distinguishing Between Proportional and Non-Proportional Situations
- 2-7: TEKS Practice
- 2-8: Additional Problem Solving
- 2-8: TEKS Practice

Topic 4: Using the Pythagorean Theorem
Topic 5: Surface Area and Volume
Topic 6: Linear Equations in One Variable
Topic 7: Reasoning in Geometry
Topic 8: Simultaneous Linear Equations

English/Spanish Glossary
Formulas
- 7-1: Angles, Lines, and Transversals
- 7-1: TEKS Practice
- 7-2: Reasoning and Parallel Lines
- 7-2: TEKS Practice
- 7-3: Interior Angles of Triangles
- 7-3: TEKS Practice
- 7-4: Exterior Angles of Triangles
- 7-4: TEKS Practice
- 7-5: Angle–Angle Triangle Similarity
- 7-5: TEKS Practice
- 7-6: Additional Problem Solving
- 7-6: TEKS Practice

- 8-1: What are Simultaneous Linear Equations in Two Variables?
- 8-1: TEKS Practice
- 8-2: Estimating Solutions of Simultaneous Linear Equations by Inspection
- 8-2: TEKS Practice
- 8-3: Solving Simultaneous Linear Equations by Graphing
- 8-3: TEKS Practice
- 8-4: Solving Simultaneous Linear Equations Using Substitution
- 8-4: TEKS Practice
- 8-5: Additional Problem Solving
- 8-5: TEKS Practice