12 5 3+(-3) + 6 3

$$12) \frac{5}{6} + \frac{3 + (-3)}{3} = \frac{5}{6} + \frac{3 - 3}{3} = \frac{5}{6} + \frac{0}{3} = \frac{5}{6} + 0 = \frac{5}{6}$$

Ответ: 5/6