2. Main Idea and New Vocabulary NGSSS
Key Concept: Subtraction Property of Equality
Example 1: Solve an Addition Equation
Key Concept: Addition Property of Equality
Example 2: Real-World Example
Example 3: Solve a Subtraction Equation
Five-Minute Check
Lesson Menu

3. Solve equations using the Subtraction and Addition Properties of Equality.
inverse operations
Main Idea/Vocabulary

4. Preparation for MA.8.A.4.2 Solve and graph one- and two-step inequalities in one variable.
NGSSS

5. Key Concept

6. Solve an Addition Equation
Solve 7 = 15 + c. Check your solution.
Method 1 Use the vertical method.
7 = c Write the equation.
– 15 = – 15 Subtraction Property of Equality
–8 = c
Method 2 Use the horizontal method.
7 = 15 + c Write the equation.
7 – 15 = 15 + c – 15 Subtraction Property of Equality
–8 = c
Example 1

7. Solve an Addition Equation
Answer: The solution is –8.
Check
7 = 15 + c Write the original equation.
7 = 15 + (–8) Replace c with –8. Is this sentence true? ?
7 = 7 The sentence is true. 
Example 1

8. Solve 9 + t = –4.
A. –13
B. –5
C. 5
D. 13
Example 1 CYP

9. Key Concept 2

10. h + (–6) = 2 Write the equation.
OCEANOGRAPHY At high tide, the top of a coral formation is 2 feet above the surface of the water. This represents a change of –6 feet from the height of the coral above the water at low tide. Write and solve an equation to determine h, the height of the coral above the water at low tide.
Let h represent the height of the coral at high tide. So, h + (–6) = 2.
h + (–6) = 2 Write the equation.
= + 6 Addition Property of Equality
h = 8 Simplify.
Example 2

11. Answer: The height of the coral at low tide is 8 feet.
Example 2

12. TEMPERATURE The temperature at 11:00 P. M. was 54°F
TEMPERATURE The temperature at 11:00 P.M. was 54°F. This represents a change of –8° from the temperature at 9:00 P.M. Write and solve an equation to determine t, the temperature at 9:00 P.M.
A. 54 – 8 = t; 46°F
B t = 8; –46°F
C. –8t = 54; –6.75°F
D. t + (–8) = 54; 62°F
Example 2 CYP

13. Solve a Subtraction Equation
Solve –5 = z – 16.
Method 1 Use the vertical method.
–5 = z – 16 Write the equation.
+ 16 = Addition Property of Equality
11 = z
Method 2 Use the horizontal method.
–5 = z – 16 Write the equation.
– = z – Addition Property of Equality
11 = z
Example 3

14. Solve a Subtraction Equation
Answer: The solution is 11.
Example 3

15. Solve r – 2 = 14.
A. –12
B. –7
C. 12
D. 16
Example 3 CYP

16. Solve −3 + b = −7. Check your solution.
A. –10
B. −4
C. 3
D. 4
Five Minute Check 1

17. Solve c − 13 = 2. Check your solution.
A. –15
B. –11
C. 11
D. 15
Five Minute Check 2

18. Solve x + 4 = 9. Check your solution.
A. –5
B. 5
C. 13
D. 36
Five Minute Check 3

19. Solve 28 = −11 + b. Check your solution.
A. 39
B. 17
C. –17
D. –39
Five Minute Check 4

20. If you increase a number by 9, the result is 26
If you increase a number by 9, the result is 26. Write and solve an equation to find the number.
A. n + 9 = 26; n = 17
B. 9n = 26; n = 2.8
C. n – 26 = 9; n = 35
D = 26; n = 234 __ n 9
Five Minute Check 5

21. Pam opened a checking account with $200
Pam opened a checking account with $200. Then she wrote a check for $125. What is the current balance in Pam’s checking account?
A. −$33
B. $75
C. $83
D. $325
Five Minute Check 6