Đáp án `+` Giải thích các bước giải:

 5.

1) 39 + 7(x + 1) = 60

7(x + 1) = 60 - 39

7(x + 1) = 21

x + 1 = 21 : 7

x + 1 = 3

x = 3 - 1

x = 2.

4) 7 + 2(x - 3) = 11

2(x - 3) = 11 - 7

2(x - 3) = 4

x - 3 = 4 : 2

x - 3 = 2

x = 2 + 3

x = 5.

7) 21 - 5(x - 4) = 11

5(x - 4) = 21 - 11

5(x - 4) = 10

x - 4 = 10 : 5

x - 4 = 2

x = 2 + 4

x = 6.

10) 96 - 3(x + 1) = 42

3(x + 1) = 96 - 42

3(x + 1) = 54

x + 1 = 54 : 3

x + 1 = 18

x = 18 - 1

x = 17.

13) 100 - 7(x - 5) = 58

7(x - 5) = 100 - 58

7(x - 5) = 42

x - 5 = 42 : 7

x - 5 = 6

x = 6 + 5

x = 11.

16) 123 - 5(x + 4) = 38

5(x + 4) = 123 - 38

5(x + 4) = 85

x + 4 = 85 : 5

x + 4 = 17

x = 17 - 4

x = 13.

2) 17 + 3(x + 6) = 47

3(x + 6) = 47 - 17

3(x + 6) = 30

x + 6 = 30 : 6

x + 6 = 5

x = 5 - 6

x = -1.

5) 5 + 2(x + 4) = 65

2(x + 4) = 65 - 5

2(x + 4) = 60

x + 4 = 60 : 2

x + 4 = 30

x = 30 - 4

x = 26.

8) 21 - 3(x - 2) = 18

3(x - 2) = 21 - 18

3(x - 2) = 3

x - 2 = 3 : 3

x - 2 = 1

x = 1 + 2

x = 3.

11) 70 - 5(x - 3) = 45

5(x - 3) = 70 - 45

5(x - 3) = 25

x - 3 = 25 : 5

x - 3 = 5

x = 5 + 3

x = 8.

14) 128 - 3(x + 4) = 23

3(x + 4) = 128 - 23

3(x + 4) = 105

x + 4 = 105 : 3

x + 4 = 35

x = 35 - 4

x = 31.

17) 147 - 7(x - 13) = 98

7(x - 13) = 147 - 98

7(x - 13) = 49

x - 13 = 49 : 7

x - 13 = 7

x = 7 + 13

x = 20.