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`x+2/5=4/3`
`=>x=4/3-2/5`
`=> x= 20/15 -6/15`
`=>x= 14/15`
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`x : 3/2 =2 xx 1/5`
`=> x : 3/2= 2/5`
`=> x= 2/5 xx 3/2`
`=> x= 6/10`
`=>x= 3/5`
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Bài `5` này có `1` chút lạ ạ
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\(a,x-1\dfrac{3}{5}=2\dfrac{1}{10}\\ x-\dfrac{8}{5}=\dfrac{21}{10}\\ x=\dfrac{21}{10}+\dfrac{8}{5}\\ x=\dfrac{21}{10}+\dfrac{16}{10}\\ x=\dfrac{37}{10}\\ b,5\dfrac{1}{7}:x=4\dfrac{1}{2}\\ \dfrac{36}{7}:x=\dfrac{9}{2}\\ x=\dfrac{36}{7}:\dfrac{9}{2}\\ x=\dfrac{36}{7}\cdot\dfrac{2}{9}\\ x=\dfrac{8}{7}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(x+\dfrac{4}{15}=\dfrac{4}{12}\)
\(x=\dfrac{4}{12}-\dfrac{4}{15}\)
\(x=\dfrac{20}{60}-\dfrac{16}{60}\)
\(x=\dfrac{1}{15}\)
b) \(x-\dfrac{5}{8}=1\dfrac{2}{3}\)
\(x-\dfrac{5}{8}=\dfrac{5}{3}\)
\(x=\dfrac{5}{3}+\dfrac{5}{8}\)
\(x=\dfrac{40}{24}+\dfrac{15}{24}\)
\(x=\dfrac{55}{24}\)
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a: =>x+1/5-27/10=11/2
=>x-5/2=11/2
hay x=8
b: =>11/4+x-7/8=6
=>15/8+x=6
hay x=33/8
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1.Tìm X:
a) `x : 8 = 107,8 - 29,25`
`x:8=78,55`
`x=78,55xx8`
`x=628,4`
b) `x + 16,7 = 50,5 : 2,5`
`x+16,7=20,2`
`x=20,2-16,7`
`x=3,5`
2.Tìm X:
a) `x - 2,35 = 3,6 : 4,5`
`x-2,35=0,8`
`x=0,8+2,35`
`x=3,15`
b) `189,5 - x = 7,2 xx 14`
`189,5 - x = 100,8`
`x=189,5-100,8`
`x=88,7`
3. Tính giá trị biểu thức :
`13,5 : 4,5 xx 2,4 + (156,9 – 80,6) `
`=3xx2,4+76,3`
`=7,2+76,3`
`=83,5`
4. Tính giá trị biểu thức :
`1,25 xx 4,2 + 119,6 : 5,2 – 23,19`
`=5,25+23-23,19`
`=5,06`
5. Tính giá trị biểu thức :
`14,75 – 7,15 : 5 + 2,6 xx 3,5`
`=14,75 – 1,43 + 9,1`
`=22,42`
6. Tính nhanh
a) `3,6 xx 78 + 78 xx 6,4=78xx(3,6+6,4)=78xx10=780`
b) `80 xx 5,29 xx 1,25=(80xx1,25)xx5,29=100xx5,29=529`
![](https://rs.olm.vn/images/avt/0.png?1311)
Câu 1: Tìm x:
a) 2/5× x =(thiếu đề)
8/7: x =4/5
x=8/7:4/5
x=10/7
Câu 2: Tính bằng cách thuận tiện nhất
5/9× 8/17 + 4/9 × 8/17
=(5/9+4/9)x8/17
=1x8/17=8/17
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,x=\dfrac{13}{2}-2\\ x=\dfrac{9}{2}\\ b,x=\dfrac{4}{5}\times\dfrac{3}{4}\\ x=\dfrac{12}{20}=\dfrac{3}{5}\)
x=83/8
x + \(3\frac{1}{2}\)+ x = \(24\frac{1}{4}\)
x + \(\frac{7}{2}\)+ x = \(\frac{97}{4}\)
x + x = \(\frac{97}{4}-\frac{7}{2}\)
x X 2 = \(\frac{83}{4}\)
x = \(\frac{83}{4}:2\)
x = \(\frac{83}{8}\)