а)

12a - 1 = 25 - a

12a + a = 25 + 1

13a = 26

a = 2

б)

11/12 x - 2/3 = -3/4x - 1/2

11/12x + 3/4x = 2/3 - 1/2

11/12x + 9/12x = 4/6 - 3/6

20/12x = 1/6

1 2/3x = 1/6

5/3x = 1/6

x = 0,1

в)

5y + 15 = 10

5y = 10 - 15

5y = -5

y = -1

г)

(x + 7)/3 × 5 = 2x - 3

(5x + 35)/ 3 = 2x - 3

5x + 35 = (2x - 3) × 3

5x + 35 = 6x - 9

5x - 6x = -35 - 9

x = 44

д)

6(4x-7) - 3(5 - 8x) = 0

6(4x -7) = 3(5-8x)

2(4x - 7) = 5 - 8x

8x - 14 = 5 - 8x

8x + 8x = 5 + 14

16x = 19

x = 1,1875