Выполни задачи 2.166, 2.167, 2.169, 2.170, 2.171 про десятичные и обыкновенные дроби

Решаю задачу 2.166: a) $0,2 + \frac{1}{7} = \frac{2}{10} + \frac{1}{7} = \frac{1}{5} + \frac{1}{7} = \frac{7}{35} + \frac{5}{35} = \frac{12}{35}$ б) $\frac{5}{6} - 0,25 = \frac{5}{6} - \frac{25}{100} = \frac{5}{6} - \frac{1}{4} = \frac{10}{12} - \frac{3}{12} = \frac{7}{12}$ в) $\frac{23}{25} + 0,4 = \frac{23}{25} + \frac{4}{10} = \frac{23}{25} + \frac{2}{5} = \frac{23}{25} + \frac{10}{25} = \frac{33}{25} = 1 \frac{8}{25}$ г) $0,75 - \frac{7}{42} = \frac{75}{100} - \frac{1}{6} = \frac{3}{4} - \frac{1}{6} = \frac{9}{12} - \frac{2}{12} = \frac{7}{12}$ Решаю задачу 2.167: a) $3,45 + \frac{3}{4} = 3,45 + 0,75 = 4,2$ б) $\frac{11}{20} - 0,25 = 0,55 - 0,25 = 0,3$ в) $2,7 + \frac{23}{25} = 2,7 + 0,92 = 3,62$ г) $1,1 - \frac{7}{8} = 1,1 - 0,875 = 0,225$ Решаю задачу 2.169: a) $\frac{23}{24} + (\frac{1}{6} + \frac{1}{4}) = \frac{23}{24} + (\frac{2}{12} + \frac{3}{12}) = \frac{23}{24} + \frac{5}{12} = \frac{23}{24} + \frac{10}{24} = \frac{33}{24} = \frac{11}{8} = 1\frac{3}{8}$ б) $\frac{4}{35} + (\frac{3}{5} + \frac{4}{7}) = \frac{4}{35} + (\frac{21}{35} + \frac{20}{35}) = \frac{4}{35} + \frac{41}{35} = \frac{45}{35} = \frac{9}{7} = 1\frac{2}{7}$ в) $\frac{11}{15} - (\frac{2}{3} - \frac{3}{20}) = \frac{11}{15} - (\frac{40}{60} - \frac{9}{60}) = \frac{11}{15} - \frac{31}{60} = \frac{44}{60} - \frac{31}{60} = \frac{13}{60}$ г) $\frac{5}{18} + (\frac{2}{9} + \frac{1}{27}) = \frac{5}{18} + (\frac{6}{27} + \frac{1}{27}) = \frac{5}{18} + \frac{7}{27} = \frac{15}{54} + \frac{14}{54} = \frac{29}{54}$ Решаю задачу 2.170: a) $\frac{7}{40} + \frac{11}{60} = \frac{21}{120} + \frac{22}{120} = \frac{43}{120}$ б) $\frac{27}{56} - \frac{5}{42} = \frac{81}{168} - \frac{20}{168} = \frac{61}{168}$ в) $\frac{11}{72} - \frac{7}{54} = \frac{33}{216} - \frac{28}{216} = \frac{5}{216}$ г) $\frac{16}{45} + \frac{17}{60} = \frac{64}{180} + \frac{51}{180} = \frac{115}{180} = \frac{23}{36}$ Решаю задачу 2.171: a) $19 - 25 \cdot (\frac{2}{5} + \frac{1}{2}) = 19 - 25 \cdot (\frac{4}{10} + \frac{5}{10}) = 19 - 25 \cdot \frac{9}{10} = 19 - \frac{225}{10} = 19 - 22,5 = -3,5$ б) $(\frac{11}{3} - \frac{15}{9}) : 2 + \frac{7}{30} = (\frac{33}{9} - \frac{15}{9}) : 2 + \frac{7}{30} = \frac{18}{9} : 2 + \frac{7}{30} = 2 : 2 + \frac{7}{30} = 1 + \frac{7}{30} = 1\frac{7}{30}$