6) 11 - 12 5 ; 18

6) $$\frac{11}{12} - \frac{5}{18}$$

$$\frac{11}{12} - \frac{5}{18} = \frac{11 \cdot 3}{12 \cdot 3} - \frac{5 \cdot 2}{18 \cdot 2} = \frac{33}{36} - \frac{10}{36} = \frac{23}{36}$$

Ответ: $$\frac{23}{36}$$