451. Найдите значение выражения: 1) 12 : 3 3/8 − 1 1/4 : 15/32; 2) 1 31/35 : (2 − 8/9 : 1 19/45); 3) (1 1/35 : 4/5 − 1 8/35) : 3 1/3; 4) (7 − 1 5/9 : 7/24) : 20/27.

1. \(12 : 3\frac{3}{8}-1\frac{1}{4}:\frac{15}{32}=\frac{32}{9}-\frac{8}{3}=\frac{8}{9}\).
2. \(1\frac{31}{35}:\left(2-\frac{8}{9}:1\frac{19}{45}\right)=\frac{66}{35}:\left(2-\frac{5}{8}\right)=\frac{66}{35}:\frac{11}{8}=\frac{48}{35}\).
3. \(\left(1\frac{1}{35}:\frac45-1\frac{8}{35}\right):3\frac13=\left(\frac97-\frac{78}{35}\right):\frac{10}{3}=-\frac{99}{350}\).
4. \(\left(7-1\frac59:\frac7{24}\right):\frac{20}{27}=\left(7-\frac{16}{3}\right):\frac{20}{27}=\frac53\cdot\frac{27}{20}=\frac94\).

Ответ: 1) \(\frac89\); 2) \(\frac{48}{35}\); 3) \(-\frac{99}{350}\); 4) \(\frac94\).