№9. Вычислите: 1) 4/25 + 15/4; 2) 9/4 + 8/5; 3) 1/5 − 27/20; 13) (3/4 − 1/6) · 3; 14) (3/20 + 7/30) · 15; 15) (1 11/16 − 3 3/8) · 4; 25) 7,9 + 2,2; 26) 6,9 + 7,4; 27) 4,4 − 1,7.

1. \(\frac{4}{25}+\frac{15}{4}=\frac{16}{100}+\frac{375}{100}=\frac{391}{100}=3\frac{91}{100}\).
2. \(\frac{9}{4}+\frac{8}{5}=\frac{45}{20}+\frac{32}{20}=\frac{77}{20}=3\frac{17}{20}\).
3. \(\frac{1}{5}-\frac{27}{20}=\frac{4}{20}-\frac{27}{20}=-\frac{23}{20}=-1\frac{3}{20}\).
4. \(\left(\frac{3}{4}-\frac{1}{6}\right)\cdot3=\frac{7}{12}\cdot3=\frac{7}{4}=1\frac{3}{4}\).
5. \(\left(\frac{3}{20}+\frac{7}{30}\right)\cdot15=\frac{23}{60}\cdot15=\frac{23}{4}=5\frac{3}{4}\).
6. \(\left(1\frac{11}{16}-3\frac{3}{8}\right)\cdot4=\left(\frac{27}{16}-\frac{54}{16}\right)\cdot4=-\frac{27}{16}\cdot4=-\frac{27}{4}=-6\frac{3}{4}\).
7. \(7.9+2.2=10.1\).
8. \(6.9+7.4=14.3\).
9. \(4.4-1.7=2.7\).

Ответ: 1) \(\frac{391}{100}\); 2) \(\frac{77}{20}\); 3) \(-\frac{23}{20}\); 13) \(\frac{7}{4}\); 14) \(\frac{23}{4}\); 15) \(-\frac{27}{4}\); 25) 10,1; 26) 14,3; 27) 2,7.