Download Lesson 2.7 Subtraction Equations

2-7 Subtraction Equations
Warm Up
Problem of the Day
Lesson Presentation
Lesson Quizzes
2-7 Subtraction Equations
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
2-7 Subtraction Equations
Problem of the Day
Bruce has 25 CDs remaining after giving
14 to John, 17 to Mary, and 25 to Sue.
How many CDs did he begin with?
81
2-7 Subtraction Equations
Sunshine State Standards
MA.6.A.3.2 Write [and] solve…one-step
linear equations…
2-7 Subtraction Equations
When Theodore Roosevelt became president
of the United States, he was 42 years old. He
was 27 years younger than Ronald Reagan
was when Reagan became president. How old
was Reagan when he became president?
2-7 Subtraction Equations
Let a represent Ronald Reagan’s age.
Ronald
Reagan’s age
a
–
27
=
Theodore
Roosevelt’s age
–
27
=
42
a – 27 = 42
+ 27 + 27
a
= 69
Ronald Reagan was 69 years old when he became
president.
2-7 Subtraction Equations
Additional Example 1A: Solving Subtraction
Equations
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.
2-7 Subtraction Equations
Additional Example 1B: Solving Subtraction
Equations
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 
Substitute 93 for s in the equation.
93 is the solution.
2-7 Subtraction Equations
Additional Example 1C: Solving Subtraction
Equations
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 
Substitute 15 for z in the equation.
15 is the solution.
2-7 Subtraction Equations
Additional Example 1D: Solving Subtraction
Equations
Solve 7 = b – 7. Check your answer.
7=b–7
+7
+7
14 = b
7 is subtracted from b.
Add 7 to both sides to undo the
subtraction.
Check 7 = b – 7
?
7 = 14 – 7
?
7=7 
Substitute 14 for b in the equation.
14 is the solution.
2-7 Subtraction Equations
Check It Out : 1A
Solve the equation. Check your answer.
57 = c – 13
57 = c - 13
+13
+13
70 = c
2-7 Subtraction Equations
Check It Out : 1B
Solve the equation. Check your answer.
g - 62 = 14
g - 62 = 14
+62 +62
g = 76
2-7 Subtraction Equations
Check It Out : 1C
Solve the equation. Check your answer.
49 = n - 11
49 = n - 11
+11
+11
60 = n
2-7 Subtraction Equations
Check It Out : 1D
Solve the equation. Check your answer.
p - 38 = 40
p - 38 = 40
+ 38 +38
p
= 78
2-7 Subtraction Equations
Check It Out : 1E
Solve the equation. Check your answer.
Floridian Nancy Rios represented the United
States in windsurfing at the 2008 Olympics. In 10
races, her best finish was 22nd place. Her best
finish was 5 places ahead of her worst finish.
Solve the equation w - 5 = 22 to determine her
worst finish.
w - 5 = 22
+5 +5
w = 27
Her worst finish was 27th place.
2-7 Subtraction Equations
Check It Out : 1F
The Great Bay Scallop Search is one of Tampa
Bay’s most popular volunteer events each year.
Volunteers snorkel to count scallops and document
the population trend.
In 2005, the search resulted in only one scallop!
This was 26 fewer scallops than were found in
1998. Write and solve a subtraction equation to
find the number of scallops found in 1998.
s - 26 =
1
+26
+26
w = 27
27 scallops were found in 1998.
2-7 Subtraction Equations
Check It Out : 1G
The Great Bay Scallop Search is one of Tampa
Bay’s most popular volunteer events each year.
Volunteers snorkel to count scallops and document
the population trend.
In 2007, 555 scallops were found. This Shattered
the previous high by 476 scallops. Before 2007,
what was the previous high number of scallops
found?
79 scallops
2-7 Subtraction Equations
Lesson Quizzes
Standard Lesson Quiz
Lesson Quiz for Student Response Systems
2-7 Subtraction Equations
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 heights is 4 inches. James is 62 inches tall.
How tall is Susan?
66 inches
2-7 Subtraction Equations
Lesson Quiz for Student Response Systems
1. Solve the equation x – 17 = 36.
A. x = 19
B. x = 21
C. x = 36
D. x = 53
2-7 Subtraction Equations
Lesson Quiz for Student Response Systems
2. Solve the equation 20 = x – 6.
A. x = 14
B. x = 20
C. x = 26
D. x = 40
2-7 Subtraction Equations
Lesson Quiz for Student Response Systems
3. Solve the equation y – 16 = 33.
A. y = 59
B. y = 49
C. y = 23
D. y = 17
2-7 Subtraction Equations
Lesson Quiz for Student Response Systems
4. Solve the equation 52 = y – 23.
A. y = 29
B. y = 31
C. y = 75
D. y = 84
2-7 Subtraction Equations
Lesson Quiz for Student Response Systems
5. Solve the equation x – 15 = 22.
A. x = 43
B. x = 37
C. x = 13
D. x = 7
2-7 Subtraction Equations
Lesson Quiz for Student Response Systems
6. During an NBA playoff game, Brand
scored 12 points more than Cassell. If
Cassell had 33 points how many points did
Brand score?
A. 45 points
B. 33 points
C. 21 points
D. 12 points