Представьте в виде дроби: a) $$rac{x}{2} + \frac{y}{3}$$; б) $$rac{c}{4} - \frac{d}{12}$$; в) $$rac{a}{b} - \frac{b^2}{a}$$; г) $$rac{3}{2x} - \frac{2}{3x}$$; д) $$rac{5x}{8y} + \frac{x}{4y}$$; ж) $$rac{1}{5a} - \frac{8}{25a}$$; з) $$rac{3b}{4c} + \frac{c}{2b}$$

Решим каждый пример по отдельности:

a) $$rac{x}{2} + \frac{y}{3} = \frac{3x}{6} + \frac{2y}{6} = \frac{3x + 2y}{6}$$

б) $$rac{c}{4} - \frac{d}{12} = \frac{3c}{12} - \frac{d}{12} = \frac{3c - d}{12}$$

в) $$rac{a}{b} - \frac{b^2}{a} = \frac{a^2}{ab} - \frac{b^3}{ab} = \frac{a^2 - b^3}{ab}$$

г) $$rac{3}{2x} - \frac{2}{3x} = \frac{9}{6x} - \frac{4}{6x} = \frac{9 - 4}{6x} = \frac{5}{6x}$$

д) $$rac{5x}{8y} + \frac{x}{4y} = \frac{5x}{8y} + \frac{2x}{8y} = \frac{5x + 2x}{8y} = \frac{7x}{8y}$$

ж) $$rac{1}{5a} - \frac{8}{25a} = \frac{5}{25a} - \frac{8}{25a} = \frac{5 - 8}{25a} = \frac{-3}{25a}$$

з) $$rac{3b}{4c} + \frac{c}{2b} = \frac{3b \cdot b}{4c \cdot b} + \frac{c \cdot 2c}{2b \cdot 2c} = \frac{3b^2}{4bc} + \frac{2c^2}{4bc} = \frac{3b^2 + 2c^2}{4bc}$$