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2. Splash Screen

3. Solve subtraction equations
Objective
Solve subtraction equations
Example 3-3c

4. Vocabulary
None
Example 3-3c

5. Example 1 Solve an Equation by Adding
Example 2 Solve a Subtraction Equation
Example 3 Use an Equation to Solve a Problem
Lesson 3 Contents

6. Ask “what is being done to the variable?”
Write the equation.
Ask “what is being done to the variable?”
The variable is being subtracted by 5
x – 5
+ 5
= 10
+ 5
Do the inverse on each side to “undo” the subtraction
Bring down x - 5
Add 5
Bring down = 10
Add 5
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Example 3-1a

7. Use the Identity Property of Addition to add x + 0 x + 0 = 15
Bring down x
Combine “like” terms
Bring down =
Combine “like” terms
x – 5
+ 5
= 10
+ 5
Use the Identity Property of Addition to add x + 0 x
+ 0 = 15
Answer:
x = 15
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Example 3-1a

8. Answer: w = 12
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Example 3-1c

9. Ask “what is being done to the variable?”
Write the equation.
Ask “what is being done to the variable?”
The variable is being subtracted by 5
x – 5
+ 5
= -1
+ 5
Do the inverse on each side to “undo” the subtraction
Bring down x - 5
Add 5
Bring down = -1
Add 5
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Example 3-2a

10. Use the Identity Property of Addition to add x + 0 x + 0 = 4
Bring down x
Combine “like” terms
Bring down =
Combine “like” terms
x – 5
+ 5
= -1
+ 5
Use the Identity Property of Addition to add x + 0 x
+ 0 = 4
Answer:
x = 4
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Example 3-2a

11. Answer: d = 3
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Example 3-2b

12. What is the record high temperature in degrees Fahrenheit?
The difference between the record high and the record low temperatures in Oregon is 173F. The record low temperature is –54F.
What is the record high temperature in degrees Fahrenheit?
Difference = high - low
Determine process to use
173 = x
The word “difference” tells us we need to subtract
Replace “difference” with 173
Bring down =
Replace “high” with variable
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Example 3-3a

13. What is the record high temperature in degrees Fahrenheit?
The difference between the record high and the record low temperatures in Oregon is 173F. The record low temperature is –54F.
What is the record high temperature in degrees Fahrenheit?
Difference = high - low
Bring down -
173 = x -
(- 54)
Replace “low” with -54
Remember: With 2 negative signs, put them together to make addition
173 = x + 54
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Example 3-3a

14. Ask “what is being done to the variable?”
Difference = high - low
The variable is being added by 54
173 = x - (- 54)
173 = x + 54
Do the inverse on each side to “undo” the addition
173
- 54
= x + 54
- 54
Bring down 173
Subtract 54
Bring down = x + 54
Subtract 54
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Example 3-3a

15. Use the Identity Property of Addition to add x + 0 173 - 54 = x + 54
Combine “like” terms
Difference = high - low
Bring down = x
173 = x - (- 54)
Combine “like” terms
173 = x + 54
Use the Identity Property of Addition to add x + 0
173
- 54
= x + 54
- 54
Add dimensional analysis
119
= x
+ 0
What is the record high temperature in degrees Fahrenheit?
Answer:
= x
0 F
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Example 3-3a

16. NOTE: Could also be 33 years = x*
The difference between the age of Julie’s mother and Julie’s age is 27 years. Julie’s age is 6. What is the age of Julie’s mother?
Answer: x = 33 years
NOTE: Could also be 33 years = x
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Example 3-3c

17. Solving Subtraction Equations
Assignment
Lesson 9:3
Solving Subtraction Equations
All
End of Lesson 3