O) \(6 \frac{7}{9} + \frac{8}{9} = 6 + \frac{7}{9} + \frac{8}{9} = 6 + \frac{15}{9} = 6 + 1 \frac{6}{9} = 7 \frac{2}{3}\)
M) \(3 \frac{4}{7} + 7 \frac{3}{7} = (3 + 7) + (\frac{4}{7} + \frac{3}{7}) = 10 + \frac{7}{7} = 10 + 1 = 11\)
Ш) \(9 \frac{9}{35} + 7 = 16 \frac{9}{35}\)