6)-3-(-1)-(-3)-(-7)

$$6) -\frac{1}{3} - (-\frac{1}{27}) \cdot (-3) - (-7) = -\frac{1}{3} - \frac{1}{27} \cdot 3 + 7 = -\frac{1}{3} - \frac{1}{9} + 7 = -\frac{1 \cdot 3}{3 \cdot 3} - \frac{1}{9} + 7 = -\frac{3}{9} - \frac{1}{9} + 7 = -\frac{4}{9} + 7 = 6\frac{5}{9}$$

Ответ: $$6\frac{5}{9}$$