Вычисли значение выражения 15*(3/20+7/30)

1. $15\cdot(\frac{3}{20}+\frac{7}{30}) = 15\cdot(\frac{9}{60}+\frac{14}{60}) = 15 \cdot \frac{23}{60} = \frac{15 \cdot 23}{60} = \frac{365}{60} = \frac{23}{4} = 5,75$ 2. $\frac{9,5+8,9}{2,3} = \frac{18,4}{2,3} = 8$ 3. $\frac{7,5+3,5}{2,5} = \frac{11}{2,5} = 4,4$ 4. $6,4 - 7 - (-3,3) = 6,4 - 7 + 3,3 = 2,7$ 5. $5,3 - 9 - (-4,4) = 5,3 - 9 + 4,4 = 0,7$ 6. $\frac{1,2}{1-\frac{1}{3}} = \frac{1,2}{\frac{2}{3}} = 1,2 \cdot \frac{3}{2} = \frac{1,2 \cdot 3}{2} = \frac{3,6}{2} = 1,8$ 7. $\frac{3}{4} + \frac{7}{25} = \frac{3 \cdot 25 + 7 \cdot 4}{100} = \frac{75 + 28}{100} = \frac{103}{100} = 1,03$ 8. $\frac{11}{4} + \frac{6}{5} = \frac{11 \cdot 5 + 6 \cdot 4}{20} = \frac{55 + 24}{20} = \frac{79}{20} = 3,95$ 9. $\frac{1,8}{1+\frac{1}{11}} = \frac{1,8}{\frac{12}{11}} = 1,8 \cdot \frac{11}{12} = \frac{1,8 \cdot 11}{12} = \frac{19,8}{12} = 1,65$ 10. $\frac{21}{17,5-0,8} = \frac{21}{16,7} \approx 1,257$ 11. $\frac{24}{4 \cdot 4,8} = \frac{24}{19,2} = 1,25$ 12. $14\cdot(\frac{1}{7})^2 - 23\cdot\frac{1}{7} = 14 \cdot \frac{1}{49} - \frac{23}{7} = \frac{14}{49} - \frac{23}{7} = \frac{2}{7} - \frac{23}{7} = -\frac{21}{7} = -3$ 13. $9\cdot(\frac{1}{9})^2 - 19\cdot\frac{1}{9} = 9 \cdot \frac{1}{81} - \frac{19}{9} = \frac{9}{81} - \frac{19}{9} = \frac{1}{9} - \frac{19}{9} = -\frac{18}{9} = -2$ 14. $\frac{6,1-7,2}{2,2} = \frac{-1,1}{2,2} = -0,5$ 15. $\frac{7,2}{8,3-8,6} = \frac{7,2}{-0,3} = -24$ **Ответы:** 1. 5,75 2. 8 3. 4,4 4. 2,7 5. 0,7 6. 1,8 7. 1,03 8. 3,95 9. 1,65 10. $\approx$ 1,257 11. 1,25 12. -3 13. -2 14. -0,5 15. -24