a: \(\Leftrightarrow2x=\dfrac{19}{5}:\dfrac{3}{32}=\dfrac{608}{15}\)

hay x=304/15

b: \(\Leftrightarrow0.25x=20\)

hay x=80

c: \(\Leftrightarrow x=\dfrac{1}{100}:\dfrac{5}{2}=\dfrac{2}{500}=\dfrac{1}{250}\)

d: \(\Leftrightarrow0.1x=\dfrac{2}{3}:\dfrac{5}{3}=\dfrac{2}{5}\)

hay \(x=\dfrac{2}{5}:\dfrac{1}{10}=\dfrac{20}{5}=4\)

Bài 1 :

Áp dụng t.c tỉ lệ thức là làm dc thôi bn

Bài 2 :

Đặt :

\(\dfrac{x}{4}=\dfrac{y}{7}=k\)\(\Leftrightarrow\left\{{}\begin{matrix}x=4k\\y=7k\end{matrix}\right.\)\(\left(1\right)\)

Thay \(xy=112\) vào \(\left(1\right)\) ta có :

\(4k.7k=112\)

\(\Leftrightarrow28k^2=112\)

\(\Leftrightarrow k^2=4\)

\(\Leftrightarrow\left[{}\begin{matrix}k^2=2^2\\k^2=\left(-2\right)^2\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}k=2\\k=-2\end{matrix}\right.\)

+) \(k=2\)\(\Leftrightarrow\left\{{}\begin{matrix}x=4.2=8\\y=7.2=14\end{matrix}\right.\)

+) \(k=-2\)\(\Leftrightarrow\left\{{}\begin{matrix}x=4.\left(-2\right)=-8\\y=7.\left(-2\right)=-14\end{matrix}\right.\)

Vậy ..

( x - 1,75 ) : 0,01 /20 = 1025

( x - 1,75 ) : 0,01 = 20500

x - 1,75 = 205

x = 206,75

x = 206,75 bạn ạ

2,5 x 0,01

= 0,025

0,025

0,025

Hình như sai đề ~ pải ko ạ

\(\dfrac{0,375-0,3+\dfrac{3}{11}+\dfrac{3}{12}}{-0,53+0,5-\dfrac{5}{11}-\dfrac{5}{12}}+\dfrac{1,5+1-0,75}{2,5+\dfrac{5}{3}-1,25}.\)

\(=\dfrac{\dfrac{3}{8}-\dfrac{3}{10}+\dfrac{3}{11}+\dfrac{3}{12}}{-\dfrac{53}{100}+\dfrac{1}{2}-\dfrac{5}{11}-\dfrac{5}{12}}+\dfrac{\dfrac{3}{2}+1-\dfrac{3}{4}}{\dfrac{5}{2}+\dfrac{5}{3}-\dfrac{5}{4}}.\)

\(=\dfrac{\dfrac{263}{440}}{\dfrac{-1487}{1650}}+\dfrac{\dfrac{7}{4}}{\dfrac{35}{12}}=\dfrac{-3945}{5948}+\dfrac{3}{5}=\dfrac{-1881}{29740}.\)