a)( 6$\frac{4}{9}$ + 3$\frac{7}{11}$ )- 4$\frac{4}{9}$
=( 6$\frac{4}{9}$ - 4$\frac{4}{9}$) +3$\frac{7}{11}$
=2+3$\frac{7}{11}$
=5$\frac{7}{11}$
b)-1$\frac{1}{3}$ -2$\frac{5}{6}$.$\frac{11}{6}$ +3:5%
=$\frac{-4}{3}$-$\frac{17}{6}$.$\frac{11}{6}$+3:$\frac{1}{20}$
=$\frac{-4}{3}$-$\frac{17}{11}$+3.20
=$\frac{-44}{33}$-$\frac{68}{33}$+60
=$\frac{-112}{33}$+60
=$\frac{1868}{33}$
c)$\frac{2}{3.5}$ +$\frac{2}{5.7}$+....+$\frac{2}{97.99}$
=$\frac{1}{3}$-$\frac{1}{5}$+$\frac{1}{5}$-$\frac{1}{7}$+...+$\frac{1}{97}$-$\frac{1}{99}$
=$\frac{1}{3}$-$\frac{1}{99}$'
=$\frac{32}{99}$
d)tự làm nốt
