287. Выполните действия: a) 3+8;. б) 10 – 3; г) 8-4; e) 7-2; ж) 7-; 3) 10-3

a) $$3+8\frac{5}{12} = 3 + \frac{8 \cdot 12 + 5}{12} = 3 + \frac{96 + 5}{12} = 3 + \frac{101}{12} = 3 + 8\frac{5}{12} = 11\frac{5}{12}$$

Ответ: $$11\frac{5}{12}$$

б) $$10\frac{6}{7} - 3 = 7\frac{6}{7}$$

Ответ: $$7\frac{6}{7}$$

г) $$8\frac{7}{12} - 4\frac{2}{12} = (8-4) + (\frac{7}{12} - \frac{2}{12}) = 4 + \frac{7-2}{12} = 4 + \frac{5}{12} = 4\frac{5}{12}$$

Ответ: $$4\frac{5}{12}$$

e) $$7\frac{5}{9} - 2\frac{8}{9} = (7-2) + (\frac{5}{9} - \frac{8}{9}) = 5 - \frac{3}{9} = 5 - \frac{1}{3} = 4\frac{3}{3} - \frac{1}{3} = 4\frac{2}{3}$$

Ответ: $$4\frac{2}{3}$$

ж) $$7 - \frac{3}{8} = 6\frac{8}{8} - \frac{3}{8} = 6\frac{5}{8}$$

Ответ: $$6\frac{5}{8}$$

з) $$10 - 3\frac{7}{15} = 9\frac{15}{15} - 3\frac{7}{15} = (9-3) + (\frac{15}{15} - \frac{7}{15}) = 6 + \frac{15-7}{15} = 6 + \frac{8}{15} = 6\frac{8}{15}$$

Ответ: $$6\frac{8}{15}$$