Đổi : \(30km=3000000cm\) 

Độ dài thu nhỏ :

\(3000000:10000=300\left(cm\right)\)

Đổi : \(20m=20000mm\)

Độ dài thu nhỏ :

\(20000:5000=4000\left(mm\right)\)

Đổi \(10m=1000m\)

Độ dài thu nhỏ :

\(1000:200=500\left(cm\right)\)

Đổi : \(2km=20000dm\)

Độ dài thu nhỏ :

\(20000:20000=1\left(dm\right)\)

Ai trl cho thì tick hết ik, gớm lại còn bày đặt 

a.\(y:\dfrac{4}{5}=\dfrac{11}{8}\)

\(y=\dfrac{11}{8}\times\dfrac{4}{5}\)

\(y=\dfrac{11}{10}\)

b.\(\dfrac{11}{3}-y=\dfrac{1}{9}\)

\(y=\dfrac{11}{3}-\dfrac{1}{9}\)

\(y=\dfrac{32}{9}\)

c.\(\dfrac{1}{7}\times x=\dfrac{8}{5}\)

\(x=\dfrac{8}{5}:\dfrac{1}{7}\)

\(x=\dfrac{56}{5}\)

\(y=\dfrac{11}{8}.\dfrac{4}{5}\)

\(y=\dfrac{44}{40}\)

\(x=\dfrac{11}{3}-\dfrac{1}{9}\)

\(x=\dfrac{99-3}{27}=\dfrac{96}{27}\)

\(x=\dfrac{8}{5}:\dfrac{1}{7}\)

\(x=\dfrac{56}{5}\)

a)\(y=\dfrac{4}{5}\times\dfrac{11}{8}=\dfrac{44}{40}=1\dfrac{4}{40}\)

b)\(y=\dfrac{11}{3}-\dfrac{1}{9}=\dfrac{33}{9}-\dfrac{1}{9}=\dfrac{32}{9}\)

c)\(x=\dfrac{8}{5}\times7=\dfrac{56}{5}\)

c)\(=\dfrac{5\times17\times2}{17\times5\times2}=1\)

\(=\dfrac{99}{33}=3\)

d)\(=4\times\dfrac{16}{3}=\dfrac{64}{3}\)

còn lại ko nhìn đc

\(1000000\times10=10000000\left(cm\right)\)

Đổi : \(10000000cm=100km\)

\(\dfrac{8}{3}-\dfrac{5}{7}=\dfrac{8\times7}{3\times7}-\dfrac{5\times3}{7\times3}=\dfrac{56}{21}-\dfrac{15}{21}=\dfrac{56-15}{21}=\dfrac{41}{21}\)

\(\dfrac{8}{3}-\dfrac{5}{7}=\dfrac{56}{21}-\dfrac{15}{21}=\dfrac{56-15}{21}=\dfrac{41}{21}\)

\(=\dfrac{56}{21}-\dfrac{15}{21}=\dfrac{41}{21}=1\dfrac{20}{21}\)

=14*17*28/270

=6664/270=3332/135

7/15+ 12/15 = 19/15

4/5 x 3/1 = 12/5

16/24- 9/24 = 7/24

1/2: 4/1 = 1/2 x 1/4= 1 /8

\(\dfrac{2}{7}+\dfrac{13}{14}=\dfrac{4}{14}+\dfrac{13}{14}=\dfrac{4+13}{14}=\dfrac{17}{14}\)

\(\dfrac{2}{7}+\dfrac{13}{14}=\dfrac{2\times2}{7\times2}+\dfrac{13}{14}=\dfrac{4}{14}+\dfrac{13}{14}=\dfrac{4+13}{14}=\dfrac{17}{14}\)