Реши примеры с дробями: 1) 15/71 + 2/9 =

Привет! Давай решим эти примеры с дробями. 1) $\frac{15}{71} + \frac{2}{9} = \frac{15 \cdot 9 + 2 \cdot 71}{71 \cdot 9} = \frac{135 + 142}{639} = \frac{277}{639}$ 2) $6 \frac{1}{12} + \frac{1}{18} = \frac{6 \cdot 12 + 1}{12} + \frac{1}{18} = \frac{73}{12} + \frac{1}{18} = \frac{73 \cdot 3 + 1 \cdot 2}{36} = \frac{219 + 2}{36} = \frac{221}{36} = 6 \frac{5}{36}$ 3) $9 \frac{1}{2} + 3 \frac{1}{7} = \frac{9 \cdot 2 + 1}{2} + \frac{3 \cdot 7 + 1}{7} = \frac{19}{2} + \frac{22}{7} = \frac{19 \cdot 7 + 22 \cdot 2}{14} = \frac{133 + 44}{14} = \frac{177}{14} = 12 \frac{9}{14}$ 4) $\frac{3}{26} - \frac{4}{39} = \frac{3 \cdot 3 - 4 \cdot 2}{78} = \frac{9 - 8}{78} = \frac{1}{78}$ 5) $12 - \frac{4}{7} = \frac{12 \cdot 7 - 4}{7} = \frac{84 - 4}{7} = \frac{80}{7} = 11 \frac{3}{7}$ 6) $11 \frac{4}{12} - \frac{1}{4} = 11 \frac{1}{3} - \frac{1}{4} = \frac{11 \cdot 3 + 1}{3} - \frac{1}{4} = \frac{34}{3} - \frac{1}{4} = \frac{34 \cdot 4 - 1 \cdot 3}{12} = \frac{136 - 3}{12} = \frac{133}{12} = 11 \frac{1}{12}$ 7) $1 \frac{1}{5} \cdot \frac{1}{6} = \frac{1 \cdot 5 + 1}{5} \cdot \frac{1}{6} = \frac{6}{5} \cdot \frac{1}{6} = \frac{1}{5}$ 8) $7 \frac{2}{3} \cdot 2 \frac{1}{4} = \frac{7 \cdot 3 + 2}{3} \cdot \frac{2 \cdot 4 + 1}{4} = \frac{23}{3} \cdot \frac{9}{4} = \frac{23 \cdot 3}{4} = \frac{69}{4} = 17 \frac{1}{4}$ 9) $2 \frac{2}{5} \cdot \frac{2}{3} = \frac{2 \cdot 5 + 2}{5} \cdot \frac{2}{3} = \frac{12}{5} \cdot \frac{2}{3} = \frac{4 \cdot 2}{5} = \frac{8}{5} = 1 \frac{3}{5}$ 10) $21 \frac{1}{4} : 5 = \frac{21 \cdot 4 + 1}{4} : 5 = \frac{85}{4} : 5 = \frac{85}{4 \cdot 5} = \frac{17}{4} = 4 \frac{1}{4}$