a) $$rac{2x + 1}{d} - \frac{3x - 2}{d} = \frac{2x + 1 - (3x - 2)}{d} = \frac{2x + 1 - 3x + 2}{d} = \frac{-x + 3}{d} = \frac{3 - x}{d}$$.
б) $$rac{x - 2y}{6a} + \frac{x + y}{2a} = \frac{x - 2y}{6a} + \frac{3(x + y)}{6a} = \frac{x - 2y + 3x + 3y}{6a} = \frac{4x + y}{6a}$$.
в) $$rac{5x - 10}{a} + \frac{6x - 12}{a} = \frac{5x - 10 + 6x - 12}{a} = \frac{11x - 22}{a}$$.
г) $$rac{12a - 36}{5b} - \frac{48 - 16a}{b} = \frac{12a - 36}{5b} - \frac{5(48 - 16a)}{5b} = \frac{12a - 36 - 240 + 80a}{5b} = \frac{92a - 276}{5b} = \frac{4(23a - 69)}{5b}$$.