1. Section 2.4 Variables and Equations
Algebra Concepts
Section 2.4
Variables and Equations

2. Equation-mathematical sentence with an equal sign
5+3=8
numerical expressions set equal
2𝑥−6=10
algebraic expression equal to a numerical
expression
4𝑥−2=5𝑥+11
algebraic expression set equal to an algebraic

3. A numerical expression set equal to a numerical expression is either true or false.
Choose True or False
#1 5− −8 =13
#2 10−20=10
# −9 =−15
# =17

4. Open sentence-an equation with one or more variables
Open sentence-an equation with one or more variables. Solution (of an equation)-value for a variable that makes an open sentence true Open sentence 𝑥+15=23 Solution 𝑥=8

5. Writing an equation from words
Identify the variable- this is the unknown
Katie is going on an airplane trip. She has 22 pounds of items in her suitcase. The airlines has a 50 pound limit on each luggage piece. How many additional pounds of items can she pack in her suitcase?
Unknown- additional pounds

6. Let 𝑥=𝑎𝑑𝑑𝑖𝑡𝑖𝑜𝑛𝑎𝑙 𝑝𝑜𝑢𝑛𝑑𝑠
𝑥+22=50
Can she take an additional 30 pounds?

7. 30+22≠50
She cannot take an additional 30 pounds.

8. When you see the word “is”, it usually gets replaced with an equal sign
The sum of five and a number is twenty-eight.
Write the equation!!!

9. If a given number is a solution, it works in the open sentence.
Equation 2𝑥+4=16 Is 6 a solution?
Substitute 6 for x.
2(6)+4 ? ?
16 = 16

10. True, False or Open Sentence
#1 12 −2 =6∙4 #2 𝑔+2𝑔−10=25 #3 He plays for the Cleveland Browns. #4 The product of three and five is eight. #5 The sum of ten and a number equals fifty.