a)
[tex](4x + 2y - 5) + (4 - 5x + 4y) = 4x + 2y - 5 + 4 - 5x + 4y = \boxed{ - x + 6y - 1}[/tex]
b)
[tex](6 {x}^{2} - 5x + 2) - (8 {x}^{2} - 6x + 7) = 6 {x}^{2} - 5x + 2 - 8 {x}^{2} + 6x - 7 = \boxed{ - 2 {x}^{2} + x - 5}[/tex]
c)
[tex](5x - 3) - ( - 4x + 2) + (6 - 2x) = 5x - 3 + 4x - 2 + 6 - 2x = \boxed{7x + 1}[/tex]
