Чему равно значение выражения: 1) $$18\frac{5}{12}-\frac{7}{12} \cdot 1\frac{19}{21}-\frac{17}{72} \cdot 2\frac{2}{3}$$

1) $$18\frac{5}{12}-\frac{7}{12} \cdot 1\frac{19}{21}-\frac{17}{72} \cdot 2\frac{2}{3} = \frac{221}{12} - \frac{7}{12} \cdot \frac{40}{21} - \frac{17}{72} \cdot \frac{8}{3} = \frac{221}{12} - \frac{2}{3} \cdot \frac{10}{3} - \frac{17}{9} \cdot \frac{1}{3} = \frac{221}{12} - \frac{20}{9} - \frac{17}{27} = \frac{221 \cdot 9 - 20 \cdot 12 - 17 \cdot 4}{108} = \frac{1989 - 240 - 68}{108} = \frac{1681}{108} = 15\frac{61}{108}$$ Ответ: $$15\frac{61}{108}$$