\(\dfrac{15}{27}=\dfrac{5}{9};\dfrac{35}{55}=\dfrac{7}{11};\dfrac{101}{909}=\dfrac{1}{9}\)

15/ 27 rút gọn thành 5/9

35/55 rút gọn thành 7/11

101/909 rút gọn thành 1/9

- Các phân số còn lại đều tối giản.

3/5 , 5/9 , 9/20 , 7/11 , 17/27 , 1/9

a: =8/5-2/3=24/15-10/15=14/15

12/20-6/18=3/5-1/3=9/15-5/15=4/15

b: 18/21-12/27=6/7-7/9=54/63-49/63=5/63

8/12-20/50=2/3-2/5=10/15-6/15=4/15

\(a,\dfrac{8}{5}-\dfrac{18}{27}=\dfrac{8}{5}-\dfrac{2}{3}=\dfrac{14}{15}\\ \dfrac{12}{20}-\dfrac{6}{18}=\dfrac{3}{5}-\dfrac{1}{3}=\dfrac{4}{15}\\ b,\dfrac{18}{21}-\dfrac{12}{27}=\dfrac{6}{7}-\dfrac{4}{9}=\dfrac{26}{63}\\ \dfrac{8}{12}-\dfrac{20}{50}=\dfrac{2}{3}-\dfrac{2}{5}=\dfrac{4}{15}\)

Ta có: \(\dfrac{21}{35}\)=\(\dfrac{21:7}{35:7}\)=\(\dfrac{3}{5}\)

Vậy \(\dfrac{3}{5}\)+\(\dfrac{5}{4}\)=\(\dfrac{12}{20}\)+\(\dfrac{25}{20}\)=\(\dfrac{37}{20}\)

\(\dfrac{9}{27}\)=\(\dfrac{9:9}{27:9}\)=\(\dfrac{1}{3}\) ; \(\dfrac{15}{20}\)=\(\dfrac{15:5}{20:5}\)=\(\dfrac{3}{4}\)

Vậy \(\dfrac{1}{3}\)+\(\dfrac{3}{4}\)=\(\dfrac{4}{12}\)+\(\dfrac{9}{12}\)=\(\dfrac{13}{12}\)

\(\dfrac{3}{9}=\dfrac{3:3}{9:3}=\dfrac{1}{3}\)

\(\dfrac{15}{27}=\dfrac{15:3}{27:3}=\dfrac{5}{9}\)

\(\dfrac{28}{20}=\dfrac{28:4}{20:4}=\dfrac{7}{5}\)

\(\dfrac{5}{105}=\dfrac{5:5}{105:5}=\dfrac{1}{21}\)

\(\dfrac{24}{39}=\dfrac{24:3}{39:3}=\dfrac{8}{13}\)

3/9=.....1/3

15/27=.....5/9

28/20=....7/5

5/105=.....1/21

24/39=.....8/13

1/3

5/9

7/5

1/21

8/13

b: 12/20+6/18=3/5+1/3=9/15+5/15=14/15

c: 8/12+20/30=2/3+2/3=4/3

d: 10/12+12/36=5/6+2/6=7/6

a: \(=3\sqrt{3}-2\sqrt{3}+4\sqrt{3}-5\sqrt{3}=2\sqrt{3}\)

là 1 nha bạn

\(\dfrac{3}{12}+\dfrac{1}{4}=\dfrac{3:3}{12:3}+\dfrac{1}{4}=\dfrac{1}{4}+\dfrac{1}{4}=\dfrac{2}{4}=\dfrac{1}{2}\)

\(\dfrac{4}{10}+\dfrac{3}{5}=\dfrac{4:2}{10:2}+\dfrac{3}{5}=\dfrac{2}{5}+\dfrac{3}{5}=\dfrac{5}{5}=1\)

\(\dfrac{12}{27}+\dfrac{2}{9}=\dfrac{12:3}{27:3}+\dfrac{2}{9}=\dfrac{4}{9}+\dfrac{2}{9}=\dfrac{6}{9}=\dfrac{2}{3}\)

\(\dfrac{7}{3}+\dfrac{20}{15}=\dfrac{7}{3}+\dfrac{20:5}{15:5}=\dfrac{7}{3}+\dfrac{4}{3}=\dfrac{11}{3}\)

i love Fairy tail