a/\(\dfrac{19}{20}-y=\dfrac{8}{5}-\dfrac{3}{4}\)
\(\dfrac{19}{20}-y=\dfrac{17}{20}\)
\(y=\dfrac{19}{20}-\dfrac{17}{20}\)
\(y=\dfrac{2}{20}=\dfrac{1}{10}\)
b/\(y:\dfrac{2}{3}=\dfrac{4}{9}\times3\)
\(y:\dfrac{2}{3}=\dfrac{4}{3}\)
\(y=\dfrac{4}{3}\times\dfrac{2}{3}\)
\(y=\dfrac{8}{9}\)

#データネ

a) 19/20 - y = 8/5 - 3/4

    19/20 - y =   17/20

                y = 17/20 + 19/20

                y =      36/20

b) y : 2/3 = 4/9 x 3

     y : 2/3 = 12/9

          y    =  12/9 x 2/3 

          y    =   24/27

tích cho mik nhaaaaaaaaaaa

Bài 1: Tìm y.

\(a)\dfrac{19}{20}-y=\dfrac{8}{5}-\dfrac{3}{4}\\ \dfrac{19}{20}-y=\dfrac{17}{20}\\ y=\dfrac{19}{20}-\dfrac{17}{20}\\ y=\dfrac{2}{20}\\ y=\dfrac{1}{10}\\ b)y:\dfrac{2}{3}=\dfrac{4}{9}\times3\\ y:\dfrac{2}{3}=\dfrac{4}{3}\\ y=\dfrac{4}{3}\times\dfrac{2}{3}\\ y=\dfrac{8}{9}\) 

Bài 2:                                      Giải:

Chiều cao của mảnh vườn đó là:

\(\dfrac{2}{3}-\dfrac{1}{4}=\dfrac{5}{12}\left(km\right)\) 

Diện tích mảnh vườn đó là:

\(\dfrac{2}{3}\times\dfrac{5}{12}=\dfrac{5}{18}\left(km^2\right)\) 

Đáp số: \(\dfrac{5}{18}km^2.\)

Bài 1

a) 19/20 - y = 8/5 - 3/4

19/20 - y = 32/20 - 15/20

19/20 - y = 17/20

y = 19/20 - 17/20

y = 2/20 = 1/10

b) y : 2/3 = 4/9 × 3

y : 2/3 = 4/3

y = 4/3 × 2/3

y = 8/3

--------------------

Bài 2

Chiều cao mảnh vườn:

2/3 - 1/4 = 5/12 (km)

Diện tích mảnh vườn:

2/3 × 5/12 = 5/18 (km²)

Bài 1: 

a) \(\dfrac{19}{20}-y=\dfrac{8}{5}-\dfrac{3}{4}\)

\(\dfrac{19}{20}-y=\dfrac{17}{20}\)

\(y=\dfrac{19}{20}-\dfrac{17}{20}\)

\(y=\dfrac{2}{20}=\dfrac{1}{10}\)

b) \(y:\dfrac{2}{3}=\dfrac{4}{9}\times3\)

\(y:\dfrac{2}{3}=\dfrac{4}{3}\)

\(y=\dfrac{4}{3}\times\dfrac{2}{3}\)

\(y=\dfrac{8}{9}\)

Bài 2: 

Giải:

Chiều cao của hình bình hành: \(\dfrac{2}{3}\times\dfrac{1}{4}=\dfrac{1}{6}\left(km\right)\)

Diện tích mảnh vườn: \(\dfrac{1}{6}\times\dfrac{2}{3}=\dfrac{1}{9}\left(km^2\right)\)

Đáp số: \(\dfrac{1}{9}km^2\)

Bài 2: 

a: \(\dfrac{4\cdot7}{9\cdot32}=\dfrac{4}{32}\cdot\dfrac{7}{9}=\dfrac{1}{8}\cdot\dfrac{7}{9}=\dfrac{7}{72}\)

b: \(\dfrac{3\cdot21}{14\cdot15}=\dfrac{63}{210}=\dfrac{3}{10}\)

c: \(\dfrac{9\cdot6-9\cdot3}{18}=\dfrac{9\cdot3}{18}=\dfrac{3}{2}\)

d: \(\dfrac{17\cdot15-17}{3-20}=\dfrac{17\cdot14}{-17}=-14\)

e: \(=\dfrac{26\cdot5}{26\cdot35}=\dfrac{5}{35}=\dfrac{1}{7}\)

f: \(=\dfrac{49\left(1+7\right)}{49}=8\)

a)y x (3+5+1)=7829+289=8118

  y x 9=8118

  y=902

Vậy y=902

b)32+19-y=28

  51-y=28

  y=51-28

  y=23

Vậy y=23

Học giỏi nhé!!! ^.^

a ) y x ( 3+5+1) = 7829 + 289

y x 9 = 8118

y = 8118 : 9 902

b  )  32 + 19 - y = 28

51 - y =28

y = 28 + 51

y = 79

\(\frac{1,3}{4}\times8-y=1\frac{2}{5}\)

\(\frac{13}{40}\times8-y=\frac{7}{5}\)

\(\frac{13}{5}-y=\frac{7}{5}\)

\(y=\frac{13}{5}-\frac{7}{5}\)

\(y=\frac{6}{5}\)

b) \(\frac{2,3}{4}\div\frac{2}{4}+y=\frac{19}{15}\)

\(\frac{23}{40}\times2+y=\frac{19}{15}\)

\(\frac{23}{20}+y=\frac{19}{15}\)

\(y=\frac{19}{15}-\frac{23}{20}\)

\(y=\frac{7}{60}\)

c)\(\dfrac{3}{8}\times\dfrac{5}{8}+y=\dfrac{5}{4}\) 

   \(\dfrac{15}{64}+y=\dfrac{5}{4}\) 

           \(y=\dfrac{5}{4}-\dfrac{15}{64}\) 

           \(y=\dfrac{65}{64}\)

d, \(\dfrac{3}{8}+\dfrac{5}{8}\times y=\dfrac{5}{4}\) 

          \(\dfrac{5}{8}\times y=\dfrac{5}{4}-\dfrac{3}{8}\) 

          \(\dfrac{5}{8}\times y=\dfrac{7}{8}\) 

                 \(y=\dfrac{7}{8}:\dfrac{5}{8}\) 

                \(y=\dfrac{7}{5}\)

a) 3/4 x y = 9/10

y = 9/10 : 3/4

y = 6/5

b) 3/5 : y = 7/20

y = 3/5 : 7/20 

y = 12/7

e)\(\dfrac{1}{3}+\dfrac{2}{3}:x=\dfrac{5}{2}\) 

       \(\dfrac{2}{3}:x=\dfrac{5}{2}-\dfrac{1}{3}\) 

       \(\dfrac{2}{3}:x=\dfrac{13}{6}\) 

             \(x=\dfrac{2}{3}:\dfrac{13}{6}\) 

             \(x=\dfrac{4}{13}\)

a) 2^x+1.3^y=12³

<=>2^x+1.3^y=(2²)³.3³

<=> 2^x+1=2⁶  và 3^y=3³

<=>x+1=6 và y=3

<=>x=5 và y=3

b) 10^x : 5^y=20^y

<=>10^x=20^y.5^y=100^y=(10²)^y

<=>x=2y (Nhiều số lắm chèn)

c) 2^x=4^y-1 

<=>2^x=2^y-2

<=>x=y-2

Mặt khác: 27^y=3^x+8

<=> 3^3y=3^x+8

<=>3y=x+8

<=>3y=(y-2)+8

<=>2y=6

<=>y=3

=>x=y-2=3-2=1

Sửa câu a xíu he

a) 2^x+1 . 3^y=12^x

<=>2^x+1.3^y=2^2x.3^x

<=>2^x+1=2^2x và 3^y=3^x

<=>x=y

và x+1=2x

<=>x=1 (và y=1)

=>Cặp (x;y)=(1;1)

a) Ta có: \(2^{x+1}\cdot3^y=12^x\)

\(\Leftrightarrow2^{x+1}\cdot3^y=\left(2^2\right)^3\cdot3^3\)

\(\Leftrightarrow\left\{{}\begin{matrix}x+1=2\cdot3\\y=3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=5\\y=3\end{matrix}\right.\)

Vậy: (x,y)=(5;3)

b) Ta có: \(10^x:5^y=20^y\)

\(\Leftrightarrow10^x=20^y\cdot5^y\)

\(\Leftrightarrow10^x=100^y\)

\(\Leftrightarrow x=2y\)