8х-(7х-142)=51
раскроем скобки
8x-7x+142 = 51
x+91 = 0
x = -91
(6-2x)+4=5x+5.5
6-2x+4 = 5x+5.5
-7x+4.5 = 0
7x-4.5 = 0
7x = 4.5
x = 0.64285714285714
9-(8x-11)=12
9-8x+11 = 12
-8x+8 = 0
8x-8 = 0
8x = 8
x = 1
8х-(7х-142)=51
раскроем скобки
8x-7x+142 = 51
x+91 = 0
x = -91
(6-2x)+4=5x+5.5
раскроем скобки
6-2x+4 = 5x+5.5
-7x+4.5 = 0
7x-4.5 = 0
7x = 4.5
x = 0.64285714285714
9-(8x-11)=12
раскроем скобки
9-8x+11 = 12
-8x+8 = 0
8x-8 = 0
8x = 8
x = 1