Решите уравнения: а) x - 4 = 8 б)

Найдем корешки. 

а) x - 4 = 8; 

x - 4 = 8;

x - 4 = -8;

x  = 8 + 4;

x = -8 + 4;

x = 12;

x = -4.

б) 1,1 - х = 1,2; 

1.1 - x = 1.2;

1.1 - x = -1.2;

x = 1.1 - 1.2;

x = 1.1 + 1.2;

x = -0.1;

x = 2.3.

в) 0,3 * х - 1 = 0,8; 

0.3 * x - 1 = 0.8;

0.3 * x - 1 = -0.8;

0.3 * x = 0.8 + 1;

0.3 * x = -0.8 + 1;

0.3 * x = 1.8;

0.3 * x = 0.2;

x = 1.8/0.3;

x = 0.2/0.3;

x = 6;

x = 2/3.

г) 1,2 + 0,4 * х = 1; 

1.2 * x + 0.4 * x = 1; 

1.2 + 0.4 * x = -1; 

12  + 4 * x = 1; 

12 + 4 * x = -1; 

4 * x = -11; 

4 * x = -13; 

x = -11/4; 

x = -13/4.