Worked-out Problems

Chapter 3 continued
11. 6 2m 8 12. 2 5 n
6 2m 6 8 6 2 5 5 n 5
2m 2
7 n
2m
2
7
n
2
2
1
1
m 1
7 n
Check: 6 2m 8 Check: 2 5 n
6 2(1) 8 2 5 7
8 8 ✓ 2 2 ✓
3.1 Guided Practice (p. 122)
1. You can use two inverse operations to solve a
two-step equation.
2. Sample answer: To solve 9 2s 15, subtract 9 from
each side.
9 2s 9 15 9
2s 6
Then divide each side by 2.
2 s
6 2 2
s 3
3. 5c 6 31
5c 6 6 31 6
5c 25
5 c
2 5
5 5
c 5
Check: 5c 6 31
5(5) 6 31
31 31 ✓
4. 2 3
t 11
2 11 3
t 11 11
9 3
t
3(9) 3 3
t
27 t
Check: 2 3
t 11
2 2 7
11
3
2 2 ✓
5. 9z 4 5
9z 4 4 5 4
9z 9
9
z
9
9
9
z 1
Check: 9z 4 5
9(1) 4 5
5 5 ✓
6. 8 8d 64
8 8d 8 64 8
8d 72
8d
72
8
8
d 9
Check: 8 8d 64
8 8(9) 64
64 64 ✓
7. (1) Total cost Cost for Cost for each Number
p
for repairs parts hour of labor of hours
(2) 168 78 45h
(3) 168 78 78 45h 78
90 45h
9 0
4 5h
45
45
2 h
It took 2 hours to repair the car.
3.1 Practice and Problem Solving (pp. 123–124)
8. 12k 7 31
12k 7 7 31 7
12k 24
1 2k
2 4
12
12
k 2
Check: 12k 7 31
12(2) 7 31
31 31 ✓
9. 13n 42 81
13n 42 42 81 42
13n 39
1 3n
3 9
13
13
n 3
Check: 13n 42 81
13(3) 42 81
81 81 ✓
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Chapter 3
Pre-Algebra 69
Worked-Out Solution Key