1)0.3(x-2)-0.2 (x+0.4)=0.6 2)4/9 (2.7m-2.1/4n)-4.2 (5/7m-0.5n) 3)m

1) Найдем корешки.

0.3 * (x - 2) - 0.2 * (x + 0.4) = 0.6; 

Скобки раскроем.

0.3 * x 0.6 0.2 * x 1.2 = 0.6; 

0,1 * x 1.8 = 0.6;

0.1 * x = 0.6 + 1.8;

0.1 * x = 2.4;

x = 2.4/0.1;

x = 24/1;

x = 24.

2) Упростим:

4/9 * (2.7 * m - 2.1/4 * n) - 4.2 * (5/7 * m - 0.5 * n);

4 * 0.3 * m 4/9 * 9/4 * n 0.6 * 5 * m 4.2/2 * n;

1.2 * m n 3 * m 2.1 * n;

-1.8 * m 3.1 * n.  

3) m lt; -m;

Неверно.

4) х -  цена конфет;

x 1.3 цена печени;

Составим уравнение. 

1,2 * x + 0.8 * (x 1.3) = 5.96;

1.2 * x + 0.8 * x 1.04 = 5.96;

2 * x = 7;

x = 7/2;

x = 3.5.