1. Вычислить: 1) \(-2\frac{1}{4}\cdot12\); 2) \(-3,76-4,35\); 3) \(5-(-4)-9\); 4) \(-3\frac{3}{5}:(-1,8)\); 5) \(2\frac{2}{3}-4\frac{3}{4}\).

1. \(-2\frac{1}{4}=-\frac{9}{4}\), поэтому \(-\frac{9}{4}\cdot12=-27\).
2. \(-3,76-4,35=-8,11\).
3. \(5-(-4)-9=5+4-9=0\).
4. \(-3\frac{3}{5}=-\frac{18}{5}\), \(-1,8=-\frac{9}{5}\). Тогда \(-\frac{18}{5}:\left(-\frac{9}{5}\right)=2\).
5. \(2\frac{2}{3}-4\frac{3}{4}=\frac{8}{3}-\frac{19}{4}=\frac{32-57}{12}=-\frac{25}{12}=-2\frac{1}{12}\).

Ответ: 1) −27; 2) −8,11; 3) 0; 4) 2; 5) −2\(\frac{1}{12}\).