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[[$$ {5x-3x+2x+4x-2x-x} = {5x+(-3x)+2x+4x+(-2x)+(-x)} = {5x+4x+\underbrace{2x+(-2x)}_{=0}+(-3x)+(-x)} = {5x+\underbrace{4x+(-4x)}_{=0}} = 5x$$]]
[[$$ {5x-3x+2x+4x-2x-x} = {5x+(-3x)+2x+4x+(-2x)+(-x)} = {5x+4x+\underbrace{2x+(-2x)}_{=0}+(-3x)+(-x)} = {5x+\underbrace{4x+(-4x)}_{=0}} = 5x$$]]
[[$$ {5x-3x+2x+4x-2x-x} = {5x+(-3x)+2x+4x+(-2x)+(-x)} = {5x+4x+\underbrace{2x+(-2x)}_{=0}+(-3x)+(-x)} = {5x+\underbrace{4x+(-4x)}_{=0}} = 5x$$]]