Варіант 3. Номер 207

1) 6x + x = 28;
7x = 28;
x = 4;

2) 9x + 5x = 30 + 26;
14x = 56;
x = 4;

3) – 3x – 6x = –57 – 7;
– 9x = –63;
x = 7;

4) 0,9x + 0,4x = 4,3 + 7,4;
1,3x = 11, 7;
x = 117 : 13;
x = 9;

5) –1,6x – 0,3x = –1,8 – 5,8;
 –1,9x = –7,6;
x = 4;