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a)
(1/3-1/5)x1/4 = 1/3x1/4-1/5x1/4=1/12-1/20=1/30
(1/3-1/5)x1/4 = 2/15x1/4=1/30
b)
2/5 x 3/7 + 2/5 x 4/7= 6/35 + 8/35 = 14/35 = 2/5
2/5 x 3/7 + 2/5 x 4/7= (3/7+4/7) x 2/5 = 1 x 2/5 = 2/5
![](https://rs.olm.vn/images/avt/0.png?1311)
a: C1: (1/3-1/5)*1/4
=2/15*1/4=2/60=1/30
C2: (1/3-1/5)*1/4
=1/3*1/4-1/5*1/4
=1/12-1/20=1/30
b: C1: 2/5*3/7+2/5*4/7
=6/35+8/35=14/35=2/5
C2: 2/5*3/7+2/5*4/7
=2/5(3/7+4/7)
=2/5*1=2/5
![](https://rs.olm.vn/images/avt/0.png?1311)
5/9 : 3/x+2 = 5/3 ( Câu này mình để x + 2 dưới mẫu nhé còn nếu tách chuyển vế âm lớp 4 chưa học ! )
<=> 3/x+2 = 5/9 : 5/3
<=> 3/x+2 = 1/3
<=> x + 2 = 9 <=> x = 7
3/7 + x/35 = 4/5
<=> x/35 = 4/5 - 3/7 = 13/35
<=> x = 13
![](https://rs.olm.vn/images/avt/0.png?1311)
X + 5/9 = 4/3
X = 4/3 - 5/9
X = 7/9
X - 4/9 = 1/2
X = 1/2 + 4/9
X = 17/18
6/13 + X = 7/6
X = 7/6 - 6/13
X = 55/78
13/5 - X = 5/6
X = 13/5 - 5/6
X= 53/30
X + 5/9 = 4/3
x = 4/3 - 5/9
x = 7/9
X - 4/9 = 1/2
x = 1/2 + 4/9
x = 17/18
6/13 + X = 7/6
x = 7/6 - 6/13
x - 55/78
13/5 - X = 5/6
x = 13/5 - 5/6
x = 53/30
![](https://rs.olm.vn/images/avt/0.png?1311)
x - 4/5 = 3/7
x = 3/7 + 4/5
x = 43/35
x + 3/7 = 4/5
x = 4/5 - 3/7
x = 13/35
19/20 - x = 8/5 - 3/4
19/20 - x = 17/20
x = 19/20 - 17/20
x = 2/20 = 1/10
4/5 x X = 6/9 - 4/7
4/5 x X = 2/21
x = 2/21 : 4/5
x =5/42
x : 7/9 = 6/8
x = 6/8 x 7/9
x = 7/12
2/3 - x/6 = 6/18
x/6 = 2/3 - 6/18
x/6 = 1/3
x/6 = 2/6
=> x =2
1. x = 43/35
2. x = 13/35
3. x = 1/10
còn lại tự tính nhá
tui bận òi
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{15}{28}\)
/HT\
15/28 nha