Вычислите: 1) 6,8 − 11·(−6,1); 2) −7·(−4,7) − 6,8; 3) (1/13 − 2 3/4)·26; 4) (8/15 + 3/10)·9.

1. \(6.8-11\cdot(-6.1)=6.8+67.1=73.9\).
2. \((-7)\cdot(-4.7)-6.8=32.9-6.8=26.1\).
3. \(\left(\frac{1}{13}-2\frac{3}{4}\right)\cdot26=\left(\frac{1}{13}-\frac{11}{4}\right)\cdot26=\frac{4-143}{52}\cdot26=\frac{-139}{2}=-69.5\).
4. \(\left(\frac{8}{15}+\frac{3}{10}\right)\cdot9=\left(\frac{16}{30}+\frac{9}{30}\right)\cdot9=\frac{25}{30}\cdot9=\frac{5}{6}\cdot9=7.5\).

Ответ: 1) 73,9; 2) 26,1; 3) −69,5; 4) 7,5.