1) $$ \frac{5}{7} + \frac{2+x}{7} - \frac{5-(2+x)}{7} - \frac{3-x}{7} = \frac{5 + 2 + x - 5 + (2 + x) - 3 + x}{7} = \frac{5 + 2 + x - 5 + 2 + x - 3 + x}{7} = \frac{1 + 3x}{7} $$
Ответ: $$\frac{1+3x}{7}$$