6–3(х+1)=7–х 2,8х=8(х+2,8)

6 – 3 * (х + 1) = 7 – х;

6 - 3х - 3 = 7 - х;

-3х + х = 7 - 6 + 3;

-2х = 4;

х = 4 : (-2);

х = -2;

6 - 3 * (-2 + 1) = 7 - (-2);

6 - 3 *(-1) = 9;

6 + 3 = 9;

9 = 9; 

2,8х = 8 * (х + 2,8);

2,8х = 8х + 22,4;

2,8х - 8х = 22,4;

-5,2х = 22,4;

-х = 22,4 : 5,2;

-х = 4,307692307692308;

-х * (-1) = 4,307692307692308 * (-1);

х = -4,307692307692308;

2,8 * (-4,307692307692308) = 8 * (-4,307692307692308 + 2,8); 

-12,06153846153846 = 8 * (-1,507692307692308);

-12,06153846153846 = -12,06153846153846.