№99, а)

3(x + 4) + 6(11 - x) = 9

3x + 12 + 66 - 6x = 9

3x - 6x = 9 - 12 - 66

-3x = -69

3x = 69

x = 69 : 3

x = 23

№99, б)

8(1 - x) + 5(x - 2) = 2

8 - 8x + 5x - 10 = 2

-8x + 5x = 2 - 8 + 10

-3x = 4

x = 4 : (-3)

x = -0,75

№99, в)

7(x - 5) - 3(2x - 6) = 10

7x - 35 - 6x + 18 = 10

7x - 6x = 10 + 35 - 18

x = 27

№99, г)

5(3 - 2x) - (12 + 7x) = 0

15 - 10x - 12 -7x = 0

-10x - 7x = 0 - 15 + 12

-17x = -3

17x = 3

x = 3 : 17

x =