1. 直接写出得数。
$6+\frac{2}{5}=$
$6-\frac{2}{5}=$
$6×\frac{2}{5}=$
$6÷\frac{2}{5}=$
$\frac{3}{4}×\frac{5}{8}=$
$\frac{5}{11}+\frac{6}{11}=$
$3-\frac{7}{9}=$
$25÷\frac{5}{7}=$
$57×\frac{12}{19}=$
$\frac{17}{99}×\frac{9}{34}=$
$7.1-\frac{1}{2}=$
$2\frac{1}{4}-0.25=$
$\frac{1}{5}+\frac{4}{6}=$
$\frac{4}{27}÷\frac{4}{9}=$
$\frac{4}{25}÷\frac{10}{21}=$

$6+\frac{2}{5}=6\frac{2}{5}$
$6-\frac{2}{5}=5\frac{3}{5}$
$6×\frac{2}{5}=\frac{12}{5}=2\frac{2}{5}$
$6÷\frac{2}{5}=6×\frac{5}{2}=15$
$\frac{3}{4}×\frac{5}{8}=\frac{15}{32}$
$\frac{5}{11}+\frac{6}{11}=1$
$3-\frac{7}{9}=2\frac{2}{9}$
$25÷\frac{5}{7}=25×\frac{7}{5}=35$
$57×\frac{12}{19}=3×12=36$
$\frac{17}{99}×\frac{9}{34}=\frac{1}{22}$
$7.1-\frac{1}{2}=7.1-0.5=6.6$
$2\frac{1}{4}-0.25=2.25-0.25=2$
$\frac{1}{5}+\frac{4}{6}=\frac{1}{5}+\frac{2}{3}=\frac{3}{15}+\frac{10}{15}=\frac{13}{15}$
$\frac{4}{27}÷\frac{4}{9}=\frac{4}{27}×\frac{9}{4}=\frac{1}{3}$
$\frac{4}{25}÷\frac{10}{21}=\frac{4}{25}×\frac{21}{10}=\frac{42}{125}$

2. 在〇里填上“＞”“＜”或“=”。
$\frac{6}{7}×\frac{1}{3}〇\frac{6}{7}$
$\frac{5}{8}×\frac{8}{5}〇\frac{5}{11}×\frac{11}{5}$
$\frac{3}{4}÷\frac{3}{2}〇\frac{3}{4}÷\frac{3}{5}$
$\frac{3}{5}×\frac{25}{39}〇1$
$\frac{4}{15}÷\frac{1}{4}〇\frac{4}{15}×\frac{1}{4}$
$\frac{1}{20}×19〇\frac{1}{19}×20$

$\frac{6}{7}×\frac{1}{3}=\frac{2}{7}$
$\frac{2}{7}＜\frac{6}{7}$
$\frac{6}{7}×\frac{1}{3}＜\frac{6}{7}$
$\frac{5}{8}×\frac{8}{5}=1$
$\frac{5}{11}×\frac{11}{5}=1$
$\frac{5}{8}×\frac{8}{5}＝\frac{5}{11}×\frac{11}{5}$
$\frac{3}{4}÷\frac{3}{2}=\frac{3}{4}×\frac{2}{3}=\frac{1}{2}$
$\frac{3}{4}÷\frac{3}{5}=\frac{3}{4}×\frac{5}{3}=\frac{5}{4}$
$\frac{1}{2}＜\frac{5}{4}$
$\frac{3}{4}÷\frac{3}{2}＜\frac{3}{4}÷\frac{3}{5}$
$\frac{3}{5}×\frac{25}{39}=\frac{5}{13}$
$\frac{5}{13}＜1$
$\frac{3}{5}×\frac{25}{39}＜1$
$\frac{4}{15}÷\frac{1}{4}=\frac{4}{15}×4=\frac{16}{15}$
$\frac{4}{15}×\frac{1}{4}=\frac{1}{15}$
$\frac{16}{15}＞\frac{1}{15}$
$\frac{4}{15}÷\frac{1}{4}＞\frac{4}{15}×\frac{1}{4}$
$\frac{1}{20}×19=\frac{19}{20}$
$\frac{1}{19}×20=\frac{20}{19}$
$\frac{19}{20}＜\frac{20}{19}$
$\frac{1}{20}×19＜\frac{1}{19}×20$

3. 解方程。
$5x+2x=4.9$
$x-(\frac{3}{12}+\frac{4}{6})=\frac{1}{2}$
$x÷\frac{4}{5}=\frac{25}{28}$

第一个方程：
解：
$7x=4.9$
$x=4.9÷7$
$x=0.7$
第二个方程：
解：
$x-(\frac{1}{4}+\frac{2}{3})=\frac{1}{2}$
$x-(\frac{3}{12}+\frac{8}{12})=\frac{1}{2}$
$x-\frac{11}{12}=\frac{1}{2}$
$x=\frac{1}{2}+\frac{11}{12}$
$x=\frac{6}{12}+\frac{11}{12}$
$x=\frac{17}{12}$
第三个方程：
解：
$x=\frac{25}{28}×\frac{4}{5}$
$x=\frac{5}{7}$

4. 脱式计算。
$5-\frac{3}{7}-\frac{2}{3}$
$\frac{11}{12}+\frac{5}{8}+\frac{3}{8}+\frac{1}{12}$
$\frac{7}{9}-(\frac{1}{3}+\frac{4}{9})$

$5-\frac{3}{7}-\frac{2}{3}$
$=5-(\frac{3}{7}+\frac{2}{3})$
$=5-(\frac{9}{21}+\frac{14}{21})$
$=5-\frac{23}{21}$
$=\frac{105}{21}-\frac{23}{21}$
$=\frac{82}{21}$
$\frac{11}{12}+\frac{5}{8}+\frac{3}{8}+\frac{1}{12}$
$=(\frac{11}{12}+\frac{1}{12})+(\frac{5}{8}+\frac{3}{8})$
$=1+1$
$=2$
$\frac{7}{9}-(\frac{1}{3}+\frac{4}{9})$
$=\frac{7}{9}-\frac{4}{9}-\frac{1}{3}$
$=\frac{3}{9}-\frac{1}{3}$
$=\frac{1}{3}-\frac{1}{3}$
$=0$