一、口算。
$\frac{12}{13}+\frac{3}{13}=$ $\frac{17}{18}-\frac{4}{18}=$ $\frac{6}{15}+\frac{7}{15}=$
$\frac{7}{12}-\frac{1}{12}=$ $\frac{1}{10}+\frac{13}{10}=$ $\frac{23}{36}-\frac{11}{36}=$
$\frac{10}{7}+\frac{4}{7}=$ $\frac{16}{21}-\frac{5}{21}=$ $\frac{12}{17}+\frac{3}{17}=$
$4.2+5.08=$ $7.2÷0.36=$ $13.5-6.2-3.8=$
$0.46×20=$ $7-0.82=$ $4.9+(8.7+5.1)=$
$0.25-0.14=$ $0.48÷1.2=$ $400×7.5×2.5=$
$4.5÷9=$ $2.5×0.12=$ $(8.5-2.5)÷0.1=$
$1.7×500=$ $3.67+1.53=$ $1.5÷0.3×0.4=$
$5.6-2.3=$ $40÷0.8=$ $(4.8-3.6)×5=$
$1.44÷1.2=$ $4.05-2.87=$ $9×3.6+3.6=$

$\frac{15}{13}$ $\frac{13}{18}$ $\frac{13}{15}$
$\frac{1}{2}$ $\frac{7}{5}$ $\frac{1}{3}$
$2$ $\frac{11}{21}$ $\frac{15}{17}$
$9.28$ $20$ $3.5$
$9.2$ $6.18$ $18.7$
$0.11$ $0.4$ $7500$
$0.5$ $0.3$ $60$
$850$ $5.2$ $2$
$3.3$ $50$ $6$
$1.2$ $1.18$ $36$

二、先通分，再比较大小。
$\frac{3}{8}$和$\frac{9}{16}$ $\frac{13}{15}$和$\frac{11}{12}$ $\frac{17}{20}$和$\frac{4}{5}$

$\frac{3}{8}=\frac{6}{16}$ $\frac{9}{16}=\frac{9}{16}$ $\frac{3}{8}＜\frac{9}{16}$
$\frac{13}{15}=\frac{52}{60}$ $\frac{11}{12}=\frac{55}{60}$ $\frac{13}{15}＜\frac{11}{12}$
$\frac{17}{20}=\frac{17}{20}$ $\frac{4}{5}=\frac{16}{20}$ $\frac{17}{20}＞\frac{4}{5}$