1) 8,3 - (3,2 + x) = 12;

3.2 + x = 8.3 - 12;

3.2 + x = -3.7;

x = -3.7 - 3.2;

x = -6.9.

2) -(x - 2.25) + 4.88 = 1.3;

-(x - 2.25) = 1.3 - 4.88;

-(x - 2.25) = -3.58;

x - 2.25 = 3.58;

x = 3.58 + 2.25;

x = 5.83.