Warm-Up 1
Day 3: Expressions and Equations
Review writing expressions, evaluating expressions, and solving one-step and two-step equations.
Student Goal
I can use variables to write, evaluate, and solve math problems.
Why It Matters
Variables and equations help students prepare for 8th grade algebraic thinking and Math 1 readiness.
Warm-Up
Warm-Up 2
Which has an equals sign?
Warm-Up 3
Solve m - 5 = 12.
Short Lesson
Standard Focus
NC.8.EE: Expressions and Equations
Student-Friendly Standard Goal
I can use expressions and equations to represent unknowns and check solutions.
- An expression is a math phrase, such as 3x + 2. It does not have an equals sign.
- An equation says two expressions are equal, such as 3x + 2 = 17.
- To solve an equation, use inverse operations and then substitute the solution back to check.
Guided Examples
Guided Example 1
Solve and Check
Solve 2x + 5 = 17.
Step 1
2x + 5 = 17
What should we undo first?
Guided Example 2
Write an Expression
A movie ticket costs 9 dollars. Write an expression for the cost of t tickets.
Step 1
t tickets
What does the variable represent?
Practice
Problem 1
Evaluate 3x - 2 when x = 5.
Problem 2
Which is an expression?
Problem 3
Solve y/4 = 6.
Problem 4
True or false: a = 3 is a solution to 5a = 15.
Problem 5
A notebook costs d dollars. Which expression shows the cost of 6 notebooks?
Reflection
How are you feeling about today's skill?
Optional reflection: Why is checking a solution helpful?