一、口算。
$\frac{29}{36}+\frac{3}{36}=$ $\frac{5}{4}-\frac{3}{4}=$ $\frac{6}{12}+\frac{5}{12}=$
$\frac{19}{23}-\frac{4}{23}=$ $\frac{7}{9}+\frac{7}{9}=$ $\frac{27}{10}-\frac{3}{10}=$
$\frac{3}{8}+\frac{17}{8}=$ $\frac{17}{32}-\frac{9}{32}=$ $\frac{4}{15}+\frac{9}{15}=$
$2.5×16=$ $28.8÷4=$ $3.2-1.34-1.66=$
$2.8-0.28=$ $1.25+0.85=$ $0.8+(1.2-0.8)=$
$3.8÷0.19=$ $8.4×5=$ $(1-0.45)÷0.5=$
$8.5-3.75=$ $19.6÷0.7=$ $4÷5-0.6=$
$7.2÷0.9=$ $0.75+12.5=$ $3.8×(4-3.8)=$
$4.06×0.5=$ $0.9÷0.45=$ $0.7+0.3×3=$
$3.06+1.94=$ $1.25×0.04=$ $0.04÷0.04+0.9=$

$\frac{8}{9}$ $\frac{1}{2}$ $\frac{11}{12}$
$\frac{15}{23}$ $\frac{14}{9}$ $\frac{12}{5}$
$\frac{5}{2}$ $\frac{1}{4}$ $\frac{13}{15}$
$40$ $7.2$ $0.2$
$2.52$ $2.1$ $1.2$
$20$ $42$ $1.1$
$4.75$ $28$ $0.2$
$8$ $13.25$ $0.76$
$2.03$ $2$ $1.6$
$5$ $0.05$ $1.9$

二、先通分，再比较大小。
$\frac{11}{12}$和$\frac{9}{10}$ $\frac{20}{39}$和$\frac{7}{13}$ $\frac{5}{9}$和$\frac{7}{12}$

$\frac{11}{12}=\frac{55}{60}$ $\frac{9}{10}=\frac{54}{60}$ $\frac{11}{12}＞\frac{9}{10}$
$\frac{20}{39}=\frac{20}{39}$ $\frac{7}{13}=\frac{21}{39}$ $\frac{20}{39}＜\frac{7}{13}$
$\frac{5}{9}=\frac{20}{36}$ $\frac{7}{12}=\frac{21}{36}$ $\frac{5}{9}＜\frac{7}{12}$