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1) x + 7 = 19

x = 19 -7

x = 12

2) x + 15 = 28

x = 28 – 15

x = 13

3) x + 9 =30

x = 30 – 9

x = 21

4) 2x + 6 = 28

2x = 28 – 6

2x = 22

x = 22 : 2

x = 11

5) 2x + 10 = 36

2x = 36 - 10

2x = 26

x = 26 : 2

x = 13

6) 4x – 7 = 21

4x =21 + 7

4x = 28

x = 28 : 4

x = 7

7) 4x – 9 = 39

4x = 39 + 9

4x = 48

x = 48 : 4

x = 12

8) 5 + 5.(x+3) = 45

5.(x + 3) = 45 – 5

5.(x + 3) = 40

x + 3 = 40 : 5

x + 3 = 8

x = 5

9) 12 + 2(x+4) = 26

2.(x + 4) = 14

x + 4 = 7

x = 3

10) 25 – 20: (x + 3) =21

20: (x + 3) = 4

x + 3 = 5

x = 2

11) 30 – 15: (x + 2) = 27

15: (x + 2) = 3

x + 2 = 5

x = 3

12) 8 + 4.(x+1)² = 44

4.(x+1)² = 36

(x+1)² = 9

TH1: x + 1 = 3

         x =2

TH2: x + 1 = -3

         x = -4

13) 10 + 5.(x+2)² = 55

5.(x+2)² = 45

(x+2)² = 9

TH1: x + 2 = 3

         x = 1

TH2: x + 2 = -3

         x = -5