835. а) 1/6 + 1/9;

Для сложения дробей с разными знаменателями необходимо привести их к общему знаменателю. а) $\frac{1}{6} + \frac{1}{9} = \frac{3}{18} + \frac{2}{18} = \frac{5}{18}$ б) $\frac{2}{9} + \frac{5}{6} = \frac{4}{18} + \frac{15}{18} = \frac{19}{18} = 1\frac{1}{18}$ в) $\frac{2}{9} + \frac{3}{8} = \frac{16}{72} + \frac{27}{72} = \frac{43}{72}$ г) $\frac{2}{10} + \frac{6}{15} = \frac{1}{5} + \frac{2}{5} = \frac{3}{5}$ д) $\frac{3}{10} + \frac{2}{12} = \frac{18}{60} + \frac{10}{60} = \frac{28}{60} = \frac{7}{15}$ е) $\frac{5}{12} + \frac{4}{15} = \frac{25}{60} + \frac{16}{60} = \frac{41}{60}$ ж) $\frac{3}{4} + \frac{5}{18} = \frac{27}{36} + \frac{10}{36} = \frac{37}{36} = 1\frac{1}{36}$ з) $\frac{2}{26} + \frac{3}{39} = \frac{1}{13} + \frac{1}{13} = \frac{2}{13}$ и) $\frac{7}{34} + \frac{5}{51} = \frac{21}{102} + \frac{10}{102} = \frac{31}{102}$ к) $\frac{4}{210} + \frac{5}{140} = \frac{2}{105} + \frac{1}{28} = \frac{8}{420} + \frac{15}{420} = \frac{23}{420}$ л) $\frac{7}{450} + \frac{8}{180} = \frac{7}{450} + \frac{2}{45} = \frac{7}{450} + \frac{20}{450} = \frac{27}{450} = \frac{3}{50}$ м) $\frac{9}{180} + \frac{7}{120} = \frac{1}{20} + \frac{7}{120} = \frac{6}{120} + \frac{7}{120} = \frac{13}{120}$