13) 5x - (7x + 7) = 9 14) 2x - (6x + 1) = 9 15) 4x - (7x - 2) = 17 16) 2x+7=3x - 2(3x - 1) 17) 4 - 2(x+3)=4(x - 5) 18) 5x+3 =7x - 5(2x+1) 19) Зу - (5 - у) = 11 20) 3x-2 ＿ 2+x 21.9

13) 5x - (7x + 7) = 9

5x - 7x - 7 = 9

2x = 9+7

2x = 16

x = 8

14) 2x - (6x + 1) = 9

2x - 6x - 1 = 9

-4x = 9+1

-4x = 10

x = -2,5

15) 4x - (7x - 2) = 17

4x - 7x + 2 = 17

-3x = 17-2 = 15

x = -5

16) 2x+7=3x - 2(3x - 1)

2x + 7 = 3x - 6x + 2

2x - 3x +6x = 2 - 7

5x = -5

x = -1

17) 4 - 2(x+3)=4(x - 5)

4 - 2x - 6 = 4x - 20

4 - 6 +20 = 4x - 2x

2x = 18

x = 9

18) 5x+3 =7x - 5(2x+1)

5x + 3 = 7x - 10x -5

5x - 7x + 10x = -5 -3

8x = -8

x = -1

19) Зу - (5 - у) = 11

3y - 5 + y = 11

3y + y = 11 - 5

4y = 6

y = 1,5