гдз математика 6 клас мерзляк

Вправа 1129

1) 9(х – 1) = х + 15
9x – 9 = x + 15
9х – х = 15 + 9
8x = 24
х = 24 : 8
х = 3;

2) (11х + 14) – (5х – 8) = 25
11х + 14 – 5x + 8 = 25
11x – 5x = 25 – 14 – 8
6х = 3
х = 3 : 6
х = 0,5;

3) 12 – 4(х – 3) = 39 – 9х
12 – 4x + 12 = 39 – 9х
–4x + 9х = 39 – 24
5х = 15
x = 15 : 5
x = 3;

4) 2(3х + 5) – 3(4х – 1) = 11,8
6x + 10 – 12x + 3 = 11,8
6x – 12x = 11,8 – 10 – 3
–6x = –1,2
x = –1,2 : (–6).