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b) \(23-\frac{x}{25}=\frac{4}{5}\)
\(\frac{x}{25}=23-\frac{4}{5}\)
\(\frac{x}{25}=\frac{111}{5}=\frac{555}{25}\)
=> x = 555
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a) \(\frac{13+x}{20}=\frac{3}{4}\)
\(\Rightarrow\frac{13+x}{20}=\frac{15}{20}\)
\(\Rightarrow13+x=15\)
\(\Rightarrow\) \(x=15-13\)
\(\Rightarrow\)\(x=2\)
b)\(\frac{23-x}{25}=\frac{4}{5}\)
\(\Rightarrow\frac{23-x}{25}=\frac{20}{25}\)
\(\Rightarrow23-x=20\)
\(\Rightarrow\) \(x=23-20\)
\(\Rightarrow\) \(x=3\)
a, 13+x/20= 3/4
Suy ra: ( 13+x). 4= 20.3
Suy ra: (13+x).4=60
Suy ra: 13+x=60:4
Suy ra: 13+x=15
Suy ra: x=15-13
Suy ra: x=2
Vậy x=2
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`(13+x)/20 = 3/4`
`(13+x) xx4=3xx20`
`(13+x)xx4=60`
`13+x=60:4`
`13+x=15`
`x=15-13`
`x=2`
__
`(23-x)/25 =4/5`
`(23-x)xx5=4xx25`
`(23-x)xx5=100`
`23-x=100:5`
`23-x=20`
`x=23-20`
`x=3`
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Câu 1 sai đề.
Câu 2:
\(23-\frac{x}{25}=\frac{4}{5}\)
\(\frac{x}{25}=\frac{111}{5}\)
\(x=555\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 2:
a, \(\dfrac{5}{23}\) \(\times\) \(\dfrac{17}{26}\) + \(\dfrac{5}{23}\) \(\times\) \(\dfrac{9}{26}\)
= \(\dfrac{5}{23}\) \(\times\) ( \(\dfrac{17}{26}\) + \(\dfrac{9}{26}\))
= \(\dfrac{5}{23}\) \(\times\) \(\dfrac{26}{26}\)
= \(\dfrac{5}{23}\)
b, \(\dfrac{3}{4}\) \(\times\) \(\dfrac{7}{9}\) + \(\dfrac{7}{4}\) \(\times\) \(\dfrac{3}{9}\)
= \(\dfrac{7}{12}\) + \(\dfrac{7}{12}\)
= \(\dfrac{14}{12}\)
= \(\dfrac{7}{6}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
13+\(\frac{x}{20}\)=\(\frac{3}{4}\)
=>\(\frac{x}{20}\)=\(\frac{3}{4}-13\)
=>\(\frac{x}{20}=\frac{3}{4}-\frac{52}{4}=-\frac{49}{4}=-\frac{245}{20}\)
=>x=-245
\(23-\frac{x}{25}=45\)
\(=>\frac{x}{25}=23-45=-22=-\frac{550}{25}\)
=>x=-550
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 1+2+3+...+2018
=[(2018-1):1+1].(2018+1):2
=2018.2019:2
=2037171
b) 4+7+10+13+...+2017
=[(2017-4):3+1].(2017+4):2
=672.2021:2
=679056
c) 1+2-3-4+5+6-7-8+9+10-11-12+13+14
=(1+2-3-4)+(5+6-7-8)+(9+10-11-12)+13+14
=-4+(-4)+(-4)+13+14
=-12+27
=15
d) 23 x 75 + 25 x 23 + 180
=23 x (75+25) +180
=23 x 100 +180
=2300+180
2480
chúc ban hoc tốt nha
a) Số số hạng: ( 2018 - 1 ) : 1 + 1 = 2018
Tổng: 2018 x ( 2018 + 1 ) : 2 = 2 037 171
\(13+\frac{x}{20}=\frac{3}{4}\Leftrightarrow\frac{x}{20}=\frac{3}{4}-13\Leftrightarrow\frac{x}{20}=-12\frac{1}{4}\)
\(\Leftrightarrow\frac{x}{20}=-\frac{49}{4}\Leftrightarrow4x=20\cdot\left(-49\right)\Leftrightarrow4x=-980\)
\(\Leftrightarrow x=\left(-980\right):4\Leftrightarrow x=-245\)
\(23-\frac{x}{25}=\frac{4}{5}\Leftrightarrow\frac{x}{25}=23-\frac{4}{5}\Leftrightarrow\frac{x}{25}=22\frac{1}{5}\)
\(\Leftrightarrow\frac{x}{25}=\frac{111}{5}\Leftrightarrow5x=25\cdot111\Leftrightarrow5x=2775\)
\(\Leftrightarrow x=2775:5\Leftrightarrow x=555\)
a)13+x/20=3/4 b)23-x/25=4/5
x/20=3/4-13 x/25=23-4/5
x/20=-12,25 x/25=22,2
x=-245 x=555