2-2 Solve Addition and Subtraction Equations
Name
Date
Solve: k 12 19
k 12 12 19 12
k 7
Add 12 to isolate k.
Solve: n 17 5
n 17 17 5 17
n 22
Subtract 17 to isolate n.
Check: k 12 19
?
Substitute –7 for k.
7 12 19
19 19 True
Check: n 17 5
?
Substitute 22 for n.
22 17 5
5 5 True
Solution set: {7}
Solution set: {22}
Solve each equation. Write a justification for each step.
Then check the solutions. Write your solution. Check students’ justifications.
1. t 11 4
2. b 15 9
{15}
{24}
t 11 11 4 11
t 15
?
Check: (15) 11 4
4 4 True
5. d 1.8 3.7
6. t 2.7 4.1
{1.9}
2
1
Copyright © by William H. Sadlier, Inc. All rights reserved.
{56}
14. 2 f 13
17. 5.1 r 7.2
18. 9.1 w 1.6
{12.3}
{10.7}
6
22. 5 k 6
21. 3 j 7
or 4 11
{95
21
21 }
9
5
8. p 5.3 7.2
{9.8}
{12.5}
11. 28 b 8
12. 12 c 2
{36}
{10}
15. 1.5 h 5.1
{15}
{15}
{15}
7. b 4.6 5.2
1
or 1 10
{11
}
10
13. 11 d 4
11
7
10. c 5 10
4. y 32 47
{17}
{1.4}
2
9. a 3 6
3. g 24 7
16. 6.2 t 4.8
{6.6}
5
{11}
19. 7 a 7
3
20. 4 d 2
{27}
{14}
1
3
1
1
7
3
23. 4 2 2.5 z 3 5 24. 5 10 1.8 q 4 5
or 2 19
{79
30
30 }
Lesson 2-2, pages 42–45.
{1.2}
{0.7}
Chapter 2
41
For More Practice Go To:
Write and solve an equation for each problem.
26. A fir tree is 27 inches shorter than a pine tree.
If the fir tree is 81 inches, how high is the
pine tree?
Let j 5 Jane; j 1 25 5 119; j 5 94;
Jane saved $94.
27. Miggy uses 21 fewer bags of feed than Ernie.
If Miggy uses 60 bags of feed, how many bags
does Ernie use?
Let p 5 pine; p 27 5 81; p 5 108.
The pine tree is 108 in. high.
28. Fifteen less than a number is 54. What is
the number?
Let e 5 number of bags Ernie uses.
e 21 5 60; e 5 81; Ernie uses 81 bags.
29. Newton is 11 years younger than Ali. If
Newton is 23 years old, how old is Ali?
n 15 5 54, n 15 1 15 5 54 1 15,
n 5 39
30. Anna is 18 years older than Sheila. If Sheila is
5 years old, how old is Anna?
Let a Ali’s age. a 11 23; a 34;
Ali is 34 years old.
31. An airplane increases altitude by 2500 feet.
If the plane’s new altitude is 37,124 feet, what
was the plane’s altitude before the increase?
Let a Anna’s age; a 18 5; a 23;
Anna is 23 years old.
32. Fitz’s average speed is 12 mi/h greater than
Paul’s average speed. If Fitz’s average speed is
58 mi/h, what is Paul’s average speed?
Let a 5 old altitude. a 1 2500 5 37,124;
a 5 34,624; The plane had an altitude of
34,624 ft before the increase.
33. A garden is increased by 180 ft2 to have room
for 60 ft2 of tomatoes, 96 ft2 of zucchini, 112 ft2
of lettuce, 222 ft2 of corn, and 40 ft2 of peppers.
What was the garden’s original length if it was
11 ft longer than the width?
Let p 5 Paul’s average speed; p 1 12 5 58;
p 5 46; Paul’s average speed is 46 mi/h.
34. After a library gave 120 paperbacks,
80 magazines, and 52 hardbacks to a school,
the school had 2985 paperbacks, magazines,
and hard-covered books. How many did the
school have before the gift?
Let g 5 original garden area.
g 1 180 5 60 1 96 1 112 1 222 1 40; g 1 180 5 530;
g 5 350; Now guess and test. If ᐉ 5 11 1 w,
then ᐉ 5 25 and w 5 14. So the original length is 25 ft.
3
1
35. Solve: 4 y 6
{5}
1
B. { 2 }
A. 12
42
Chapter 2
Work backward. 2985 120 5 2865;
2865 80 5 2785; 2785 52 5 2733.
The school originally had 2733 paperbacks,
magazines, and hard-covered books.
36. Solve: 29.62 x 32
{7}
2
D. { 3 }
C. 12
F. {2.38}
H. {29.94}
G. {3.62}
J. {61.62}
Copyright © by William H. Sadlier, Inc. All rights reserved.
25. Billy saved $25 more than Jane. If Billy saved
$119, how much did Jane save?