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1-9 SolvingEquations byAdding
Preview
Warm Up
California Standards
Lesson Presentation
Holt CA Course 1
1-9 SolvingEquations byAdding
Warm Up
Solve each equation.
1. x + 7 = 22
x = 15
2. 18 + x = 105 x = 87
3. 16 = x + 9
x=7
4. 23 = x + 4
x = 19
Holt CA Course 1
1-9 SolvingEquations byAdding
California
Standards
AF1.1 Write and solve one-step
linear equations in one variable.
Holt CA Course 1
1-9 SolvingEquations byAdding
When John F. Kennedy
became president of the
United States, he was 43
years old. He was 8 years
younger than Abraham
Lincoln was when Lincoln
became President. How old
was Lincoln when he
became president?
Holt CA Course 1
1-9 SolvingEquations byAdding
Let a represent Abraham Lincoln’s age.
Abraham
Lincoln’s age
a
–
8
=
John F.
Kennedy’s age
–
8
=
43
a – 8 = 43
+8
a
+8
= 51
Abraham Lincoln was 51 years old when he became
president.
Holt CA Course 1
1-9 SolvingEquations byAdding
A
dditionalExample 1A: SolvingEquations byAdding
Solve y – 23 = 39. Check your answer.
y – 23 = 39
23 is subtracted from y.
+ 23 + 23
y
Add 23 to both sides to undo the
subtraction.
= 62
Check y – 23 = 39
?
62 – 23 = 39
?
Substitute 62 for y in the
equation.
39 = 39  62 is the solution.
Holt CA Course 1
1-9 SolvingEquations byAdding
A
dditionalExample 1B: SolvingEquations byAdding
Solve 78 = s – 15. Check your answer.
78 = s – 15
+ 15
+ 15
93 = s
15 is subtracted from s.
Add 15 to both sides to undo the
subtraction.
Check 78 = s – 15
?
78 = 93 – 15
?
78 = 78 
Holt CA Course 1
Substitute 93 for s in the
equation.
93 is the solution.
1-9 SolvingEquations byAdding
A
dditionalExample 1C: SolvingEquations byAdding
Solve z – 3 = 12. Check your answer.
z – 3 = 12
+3 +3
z
= 15
3 is subtracted from z.
Add 3 to both sides to undo the
subtraction.
Check z – 3 = 12
?
15 – 3 = 12
?
12 = 12 
Holt CA Course 1
Substitute 15 for z in the
equation.
15 is the solution.
1-9 SolvingEquations byAdding
Check It Out!Example 1B
Solve 57 = c – 13. Check your answer.
57 = c – 13
+ 13
+ 13
70 = c
13 is subtracted from c.
Add 13 to both sides to undo the
subtraction.
Check 57 = c – 13
?
57 = 70 – 13 Substitute 70 for c in the
equation.
?
57 = 57 
Holt CA Course 1
70 is the solution.
1-9 SolvingEquations byAdding
Check It Out! You try this one…
Solve g – 62 = 14. Check your answer.
g – 62 = 14
+ 62 + 62
g
= 76
62 is subtracted from g.
Add 62 to both sides to undo the
subtraction.
Check g – 62 = 14
?
76 – 62 = 14
?
Substitute 76 for g in the
equation.
14 = 14  76 is the solution.
Holt CA Course 1
1-9 SolvingEquations byAdding
Lesson Quiz
1. x – 9 = 21
x = 30
2. 14 = x – 3
x = 17
3. x – 7 = 11
x = 18
4. 16 = x – 14 x = 30
5. x – 9 = 11
x = 20
6. Susan is taller than James. The difference in
their height is 4 inches. James is 62 inches
tall. How tall is Susan?
66 inches
Holt CA Course 1