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![](https://rs.olm.vn/images/avt/0.png?1311)
a: 4/9+3/7=28/63+27/63=55/63
3/4+7/24=18/24+7/24=25/24
1/3+2/9+4/27=9/27+6/27+4/27=19/27
b: 5/6-3/8=20/24-9/24=11/24
7/15-11/30=14/30-11/30=3/30=1/10
2/3+1/6-7/12
=8/12+2/12-7/12
=3/12=1/4
c: 18/25*15/6=15/25*18/6=3*3/5=9/5
30/49:6/7=30/49*7/6=210/294=5/7
1/2*3/4:6/5=3/8*5/6=15/48=5/16
d: 8*3/5:12/5=24/5*5/12=2
4:9/5:10/3=4*5/9*3/10=2/3
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\dfrac{12}{20}\)
b)\(\dfrac{6}{21}\)
c)\(\dfrac{3}{4}\)
d) 6 ; \(\dfrac{3}{4}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\dfrac{3}{4}-\dfrac{1}{8}=\dfrac{6}{8}-\dfrac{1}{8}=\dfrac{6-1}{8}=\dfrac{5}{8}\)
b) \(\dfrac{2}{6}-\dfrac{5}{18}=\dfrac{6}{18}-\dfrac{5}{18}=\dfrac{6-5}{18}=\dfrac{1}{18}\)
c) \(\dfrac{2}{5}-\dfrac{3}{20}=\dfrac{8}{20}-\dfrac{3}{20}=\dfrac{8-3}{20}=\dfrac{5}{20}=\dfrac{1}{4}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(2:\dfrac{2}{7}+\dfrac{12}{5}=2.\dfrac{7}{2}+\dfrac{12}{5}=7+\dfrac{12}{5}=\dfrac{47}{5}\)
\(\dfrac{5}{16}:\left[\dfrac{5}{8}+\dfrac{3}{24}\right]=\dfrac{5}{16}:\dfrac{3}{4}=\dfrac{5}{16}.\dfrac{4}{3}=\dfrac{5}{12}\)
\(2:\dfrac{2}{7}+\dfrac{12}{5}=7\dfrac{12}{5}=\dfrac{47}{5}\)
\(\dfrac{5}{16}:\left(\dfrac{5}{8}+\dfrac{3}{24}\right)=\dfrac{5}{16}:\dfrac{3}{4}=\dfrac{5}{16}\cdot\dfrac{4}{3}=\dfrac{20}{48}=\dfrac{5}{12}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\dfrac{3}{5}+\dfrac{1}{6}=\dfrac{18}{30}+\dfrac{5}{30}=\dfrac{23}{30}\)
b) \(4+\dfrac{2}{5}=\dfrac{20}{5}+\dfrac{2}{5}=\dfrac{22}{5}\)
c) \(\dfrac{25}{12}-\dfrac{7}{6}=\dfrac{25}{12}-\dfrac{14}{12}=\dfrac{11}{12}\)
d) \(\dfrac{9}{7}-\dfrac{7}{6}=\dfrac{54}{42}-\dfrac{49}{42}=\dfrac{5}{42}\)
d) \(\dfrac{3}{7}\times\dfrac{2}{5}=\dfrac{3\times2}{7\times5}=\dfrac{6}{35}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\dfrac{2}{3};\dfrac{5}{8};\dfrac{24}{25}\)
b) \(\dfrac{10}{15};\dfrac{12}{18};\dfrac{18}{27}\)
\(\dfrac{ }{ }\)21/16
-21/16