a) -(a+2b) - (b-2a) = -a - 2b - b + 2a = a - 3b
b) -(4x +7y - 5) - (7y+2x) - 3y = -4x - 7y + 5 - 7y -2x - 3y = -6x - 17y + 5
c) 12(3x + 4y + 5) - 12(-3x + 4y - 5) = 36x + 48y + 60 + 36x - 48y + 60 = 72x + 120
d) [tex]-5(\frac{1}{25}x + \frac{1}{15}xy - \frac{1}{10}y) - 2(\frac{1}{10}x - \frac{1}{4}y) = -\frac{1}{5}x - \frac{1}{3}xy + \frac{1}{2}y - \frac{1}{5}x + \frac{1}{2}y = -\frac{2}{5}x - \frac{1}{3}xy + y[/tex]
e) [5(2x-4y) + 6(-10x - 15y)] : 10 = (10x - 20y - 60x - 90y) : 10 = (-50x - 110y) : 10 = [tex]\frac{-50x - 110y}{10} = \frac{10(-5x - 11y)}{10} = -5x - 11y[/tex]
