Transcript A. x

Five-Minute Check (over Lesson 12–2)
Main Idea and Vocabulary
Example 1: Solve an Equation by Subtracting
Example 2: Solve an Equation Using Zero Pairs
Key Concept: Subtraction Property of Equality
Example 3: Use an Equation to Solve a Problem
• Solve addition equations.
• inverse operations
• Subtraction Property of Equality
Solve an Equation By Subtracting
Solve x + 4 = 5.
Method 1 Use models.
Model the equation.
Remove 4 counters
from each side.
Solve an Equation By Subtracting
Method 2 Use symbols.
x+4=
5
–4=–4
x=
1
Write the equation.
Subtract 4 from each side to “undo”
the addition of 4 on the left.
5–4=1
Answer: The solution is 1.
Check
1+4=5 
Solve x + 7 = 13.
A. x = – 20
B. x = – 6
C. x = 6
D. x = 20
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B
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Solve an Equation Using Zero Pairs
Solve x + 11 = 7. Check your solution.
Method 1 Use models.
Solve an Equation Using Zero Pairs
Solve an Equation Using Zero Pairs
Method 2 Use symbols.
x + 11 =
7
– 11 = – 11
Write the equation.
Subtract 11 from each side.
x= –4
Answer: The solution is –4.
Check
x + 11 = 7
?
–4 + 11 = 7
7=7 
Write the equation.
Replace x with –4.
This sentence is true.
Solve m + 9 = 3.
A. m = –12
B. m = –6
C. m = 6
D. m = 12
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Use an Equation to Solve a
Problem
PENNSYLVANIA The width of Pennsylvania (from
north to south) is 280 miles. This is 120 miles more
than the length of the state (from east to west).
Write and solve an addition equation to find the
length of Pennsylvania.
Words
length plus 120 miles is 280 miles
Variable
Let x represent the length of Pennsylvania.
Equation x + 120 = 280
Use an Equation to Solve a
Problem
x + 120 = 280
– 120 = –120
x
= 160
Write the equation.
Subtract 120 from each side.
280 – 120 = 160
Answer: So, the length of Pennsylvania is 160 miles.
INTERNET Steve was on the Internet for 40 minutes
last night. This was 15 more minutes than Beth
spent on the Internet the same night. Write and
solve an addition equation to find the amount of
time Beth spent on the Internet last night.
A. 15 – t = 40; 20 minutes
B. 15 + t = 40; 25 minutes
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D. 40 – t = 15; 55 minutes
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C. 40 + t = 15; 25 minutes
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End of the Lesson
Five-Minute Check (over Lesson 12–2)
Image Bank
Math Tools
Solving Equations Using Addition and
Subtraction
(over Lesson 12-2)
Simplify 7 + (x + 2).
A. 7x + 14
B. 9 + x
C. 9 – x
D. 14 + x
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(over Lesson 12-2)
Simplify (x ● 4) ● 4.
A. 4x ● 16
B. 4x ● 4
C. 16x
D. 8x
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(over Lesson 12-2)
Simplify 9(6x).
A. 54x
B. 15x
C. 6x ● 9
D. 54 + x
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(over Lesson 12-2)
Simplify 7x + 2 + x.
A. 9x
B. 8x + 2
C. 7x + 2
D. 6x + 2
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(over Lesson 12-2)
Simplify 4x + 4x.
A. 8x
B. 16x
C. 0
D. 16x2
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(over Lesson 12-2)
Simplify x + 3 + 5x.
A. 8x
B. 8x2
C. 6x + 3
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D. 15x2
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(over Lesson 12-2)
Which of the following is true concerning the
expression 5x + 7 + 2x?
A. 5x and 7 are like terms.
B. The simplified form of the
expression is 5x + 9.
C. 5x and 2x are like terms.
D. The simplified form of the
expression is 14x.
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