210-x+{x-[-x+7-(x+7)]-x}=110
210-x+{x-[-x+7-x-7]-x}=110
210-x+{x+x-7+x+7-x}=110
210-x+x+x-7+x+7-x=110
210 - (x+x) + (x+x+x) + (7-7) = 110
210 - 2x + 3x + 0 = 110
(3x-2x) + 210 = 110
1x = 110 - 210
x = -100
\(210-x+\left\{x-\left[-x+7-\left(x+7\right)\right]-x\right\}=110\)
\(210-x+\left\{x-\left[-x+7-x-7\right]-x\right\}=110\)
\(210-x+\left\{x-\left[-2x\right]-x\right\}=110\)
\(210-x+2x=110\)
\(x=110-210\)
\(x=-100\)
vậy \(x=-100\)