\(\dfrac{30}{42}=\dfrac{30:6}{42:6}=\dfrac{5}{7}\)

  \(\dfrac{x}{7}=\dfrac{22}{7}\)

⇔ \(7x=154\)

⇔   \(x=22\)

\(1000:100=10\)

\(75.100=7500\)

\(900.10=9000\)

\(8.100:10:10.10000=800:10:10.10000=8.10000=80000\)

\(\dfrac{15.1}{5.72}=\dfrac{15}{360}=\dfrac{1}{24}\)

2 . 3 = 6

2 . 5 = 10

2 . 6 = 12

    \(\dfrac{32}{x}=\dfrac{-8}{3}\)

⇔ \(-8x=96\)

⇔     \(x=-12\)

     \(\dfrac{x}{8}=\dfrac{2}{x}\)

⇔  \(x^2=16\)

⇔  \(x^2=4^2\)

⇔  \(x=4\)

\(3+\dfrac{2}{3}=\dfrac{9}{3}+\dfrac{2}{3}=\dfrac{11}{3}\)

\(\dfrac{3}{4}+1=\dfrac{3}{4}+\dfrac{4}{4}=\dfrac{7}{4}\)

\(\dfrac{9}{2}-4=\dfrac{9}{2}-\dfrac{8}{2}=\dfrac{1}{2}\)

\(5-\dfrac{5}{8}=\dfrac{40}{8}-\dfrac{5}{8}=\dfrac{35}{8}\)

CT tính chu vi hình chữ nhật : \(\left(dài+rộng\right).2\)

Thay a = 119 ; b = 0 vào biểu thức M ta có :

 \(M=0:\left(119.119+2005\right)+\left(119:a-b.2005\right)\)

 \(M=0+1\)

 \(M=1\)