Решим задания с этой страницы.
### 19.18
1) $8 \frac{1}{5} - (\frac{1}{10} + \frac{1}{5} + \frac{3}{10}) = 8 \frac{2}{10} - (\frac{1}{10} + \frac{2}{10} + \frac{3}{10}) = 8 \frac{2}{10} - \frac{6}{10} = 7 \frac{12}{10} - \frac{6}{10} = 7 \frac{6}{10} = 7 \frac{3}{5}$
2) $3 : 5 - (\frac{1}{5} - \frac{1}{10}) = 0,6 - (\frac{2}{10} - \frac{1}{10}) = 0,6 - 0,1 = 0,5$
### 19.19
1) $1 \frac{1}{2} + 2 \frac{2}{3} - \frac{3}{4} + \frac{5}{6} = 1 \frac{6}{12} + 2 \frac{8}{12} - \frac{9}{12} + \frac{10}{12} = 3 \frac{14}{12} - \frac{9}{12} + \frac{10}{12} = 3 \frac{5}{12} + \frac{10}{12} = 3 \frac{15}{12} = 4 \frac{3}{12} = 4 \frac{1}{4}$
2) $9 - 2 \frac{5}{6} + 8 \frac{2}{3} - 3 \frac{3}{4} = 6 \frac{1}{6} + 8 \frac{2}{3} - 3 \frac{3}{4} = 6 \frac{2}{12} + 8 \frac{8}{12} - 3 \frac{9}{12} = 14 \frac{10}{12} - 3 \frac{9}{12} = 11 \frac{1}{12}$
3) $10 \frac{1}{2} - 9 \frac{2}{3} + \frac{1}{4} - \frac{5}{6} = 10 \frac{6}{12} - 9 \frac{8}{12} + \frac{3}{12} - \frac{10}{12} = 9 \frac{18}{12} - 9 \frac{8}{12} + \frac{3}{12} - \frac{10}{12} = \frac{10}{12} + \frac{3}{12} - \frac{10}{12} = \frac{3}{12} = \frac{1}{4}$
4) $6 \frac{2}{5} + 3 \frac{1}{2} - 2 \frac{3}{10} + \frac{3}{5} = 6 \frac{4}{10} + 3 \frac{5}{10} - 2 \frac{3}{10} + \frac{6}{10} = 9 \frac{9}{10} - 2 \frac{3}{10} + \frac{6}{10} = 7 \frac{6}{10} + \frac{6}{10} = 7 \frac{12}{10} = 8 \frac{2}{10} = 8 \frac{1}{5}$
### 19.20
1) $(20 - 19 \frac{2}{4}) + (17 \frac{3}{4} - 17) + (2 \frac{1}{2} - \frac{17}{24}) = (20 - 19 \frac{1}{2}) + \frac{3}{4} + (2 \frac{12}{24} - \frac{17}{24}) = \frac{1}{2} + \frac{3}{4} + (1 \frac{36}{24} - \frac{17}{24}) = \frac{2}{4} + \frac{3}{4} + 1 \frac{19}{24} = 1 \frac{1}{4} + 1 \frac{19}{24} = 1 \frac{6}{24} + 1 \frac{19}{24} = 2 \frac{25}{24} = 3 \frac{1}{24}$
2) $25 \frac{7}{9} - 8 \frac{3}{4} - (13 \frac{5}{12} + 2 \frac{11}{18}) + (2 \frac{1}{6} - 1 \frac{5}{9}) = 17 \frac{28-27}{36} - (13 \frac{15}{36} + 2 \frac{22}{36}) + (2 \frac{3}{18} - 1 \frac{10}{18}) = 17 \frac{1}{36} - 15 \frac{37}{36} + (1 \frac{21}{18} - 1 \frac{10}{18}) = 17 \frac{1}{36} - 16 \frac{1}{36} + \frac{11}{18} = 1 + \frac{11}{18} = 1 \frac{11}{18}$
### 19.21
1) $10 \frac{5}{6} + (5 \frac{1}{3} - 2 \frac{1}{6}) = 10 \frac{5}{6} + (5 \frac{2}{6} - 2 \frac{1}{6}) = 10 \frac{5}{6} + 3 \frac{1}{6} = 13 \frac{6}{6} = 14$
2) $12 \frac{5}{12} - (3 \frac{4}{5} + 5 \frac{5}{6}) = 12 \frac{5}{12} - (3 \frac{24}{30} + 5 \frac{25}{30}) = 12 \frac{5}{12} - 8 \frac{49}{30} = 12 \frac{5}{12} - 9 \frac{19}{30} = 11 \frac{25+5}{60} - 9 \frac{38}{60} = 11 \frac{85}{60} - 9 \frac{38}{60} = 2 \frac{47}{60}$
### 19.22 (Решения из кружочков)
1) $5 \frac{1}{2} - x = \frac{3}{8} \Rightarrow x = 5 \frac{4}{8} - \frac{3}{8} = 5 \frac{1}{8}$
2) $4 \frac{1}{2} + x = 8 \frac{3}{5} \Rightarrow x = 8 \frac{6}{10} - 4 \frac{5}{10} = 4 \frac{1}{10}$
3) $a + 1 \frac{7}{9} = 1 \frac{7}{9} \Rightarrow a = 0$
4) $x + 3 \frac{1}{3} = 10 \frac{1}{2} \Rightarrow x = 10 \frac{3}{6} - 3 \frac{2}{6} = 7 \frac{1}{6}$
5) $x - 9 \frac{2}{3} = 0 \Rightarrow x = 9 \frac{2}{3}$
### 20.1
$0,8 + 0,1 = 0,9$ | $3,9 + 0,01 = 3,91$ | $7 - 5,6 = 1,4$ | $3 + 8,6 = 11,6$
$0,8 + 0,2 = 1,0$ | $4,8 + 0,2 = 5,0$ | $8 - 0,111 = 7,889$ | $2 - 1,9 = 0,1$
$4 - 0,25 = 3,75$ | $0,3 - 0,29 = 0,01$ | $4,3 + 0,43 = 4,73$ | $6,5 - 0,99 = 5,51$
