a) (y+1/5)*3/7=5/14
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(y+\frac{1}{5}\right).\frac{3}{7}=\frac{5}{14}\)
\(\left(y+\frac{1}{5}\right)=\frac{5}{6}\)
\(y=\frac{5}{6}-\frac{1}{5}\)
\(y=\frac{19}{30}\)
Vậy \(y=\frac{19}{30}\)
\(\left(y+15\right).\frac{3}{7}=\frac{5}{14}\)
\(\Rightarrow y+15=\frac{5}{14}:\frac{3}{7}\)
\(\Rightarrow y+15=\frac{5}{6}\)
\(\Rightarrow y=\frac{5}{6}-15\)
\(\Rightarrow y=-\frac{85}{6}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) y = 5/14 : 6/7
y = 5/12
vậy y = 5/12
b) y = 4/9 x 2/3
y = 8/27
vậy t = 8/27
c) y = 1/2 - 3/10
y = 1/5
vậy y = 1/5
d) y = 5/6 - 1/3
y = 1/2
vậy y = 1/2
![](https://rs.olm.vn/images/avt/0.png?1311)
( 2 x y + 2/15 ) x 3 = 4/5
( 2 x y + 2/15 ) = 4/5 : 3
( 2 x y + 2/15 ) = 4/15
2 x y = 4/15 - 2/15
2 x y = 2/15
y = 2/15 :2
y = 1/15
(2 x y + 2/15) x 3 = 4/5
2 x y + 2/15) = 4/5 : 3
2 x y + 2/15 = 4/15
2 x y = 4/15 - 2/15
2 x y = 2/15
y = 2/15 : 2
y = 1/15
7/9 x (2 - 1/3 x y) = 14/15
(2 - 1/3 x y) = 14/15 : 7/9
(2 - 1/3 x y) = 6/5
2 - y = 6/5 x 1/3
2 - y = 2/5
y = 2/5 + 2
y = 12/5
4/21 + 5 x y - 8/7 = 1/3
4/21 + 5 x y = 1/3 + 8/7
4/21 + 5 x y = 31/21
5 x y = 31/21 - 4/21
5 x y = 9/7
y = 9/7 : 5
y = 9/35
7/12 x y - 3/12 x y = 5
y x (7/12 - 3/12) = 5
y x 1/3 = 5
y = 5 : 1/3
y = 15
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
d, \(\left(-\frac{3}{4}+\frac{2}{5}\right):\frac{3}{7}+\left[\frac{3}{5}+\left(-\frac{1}{4}\right)\right]:\frac{3}{7}\)
\(=\frac{7}{20}:\frac{3}{7}+\frac{7}{20}:\frac{3}{7}\)
\(=0\)
3/5/7 là hỗn số nhé ba năm phần bảy
tương tự như mấy câu khác nhé
![](https://rs.olm.vn/images/avt/0.png?1311)
Bai 2 :
\(\hept{\begin{cases}x+y=7\\x-7=13\end{cases}\Leftrightarrow\hept{\begin{cases}x+y=7\\x=20\end{cases}}}\)
Thay x vào phương trình đầu ta có :
\(20+y=7\Leftrightarrow y=-13\)
Vậy \(\left\{x;y\right\}=\left\{20;-13\right\}\)
Thử \(20-13=7\); \(20-7=13\)( thỏa mãn )
![](https://rs.olm.vn/images/avt/0.png?1311)
a) y : 4/11 x 3/5 = 27/4
y : 4/11 = 27/4 : 3/5
y : 4/11 = 45/4
y = 45/4 x 4/11
y = 45/11
b) y + 7/2 - 5/9 = 14/3
y + 7/2 = 14/3 + 5/9
y + 7/2 = 47/9
y = 47/9 - 7/2
y = 31/18
a) y : 4/11 x 3/5 = 27/4
y : 4/11 = 27/4 : 3/5
y : 4/11 = 45/4
y = 45/4 x 4/11
y = 45/11
b) y + 7/2 - 5/9 = 14/3
y + 7/2 = 14/3 + 5/9
y + 7/2 = 47/9
y = 47/9 - 7/2
y = 31/18
![](https://rs.olm.vn/images/avt/0.png?1311)
a, x=5y/7thay vào x-y = 1
ta đc:
5y/7 - y=1
<=> -2y=7
<=> y=-7/2
=> x=-5/2
\(\left(y+\frac{1}{5}\right).\frac{3}{7}=\frac{5}{14}\)
\(\left(y+\frac{1}{5}\right)=\frac{5}{14}:\frac{3}{7}\)
\(\left(y+\frac{1}{5}\right)=\frac{5}{6}\)
\(y=\frac{5}{6}-\frac{1}{5}\)
\(y=\frac{19}{30}\)
Vậy \(y=\frac{19}{30}\)
(y + 1/5) . 3/7 = 5/14
y + 1/5 = 5/14 : 3/7
y + 1/5 = 5/6
y = 5/6 - 1/5
y = 19/30
Chúc bạn học tốt ^^