E
[tex](12x + 8) + (5x - 8) = 12x + 8 + 5x - 8 = 17x[/tex]
M
[tex](xy - x) + (3x - xy) = xy - x + 3x - xy = 2x[/tex]
L
[tex](7 + x) + (4x - 2) = 7 + x + 4x - 2 = 5x + 5 = 5(x + 1)[/tex]
E
[tex](x - 2 {x}^{2} ) + (5x + {x}^{2} ) = x - 2 {x}^{2} + 5x + {x}^{2} = 6x - {x}^{2} [/tex]