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![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{13+x}{20}=\dfrac{15}{20}\)
\(13+x=15\)
\(x=2\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(13+\dfrac{x}{20}\text{=}\dfrac{3}{4}\)
\(\dfrac{x}{20}\text{=}\dfrac{3}{4}-13\)
Em xem lại đề nhé tại vì lớp 5 chưa học số âm ạ.
Hoặc đây có thể là đề bài bạn cần.
\(\dfrac{13+x}{20}\text{=}\dfrac{3}{4}\)
\(13+x\text{=}\dfrac{3}{4}\times20\)
\(13+x\text{=}15\)
\(x\text{=}15-13\)
\(x\text{=}2\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Câu 1 sai đề.
Câu 2:
\(23-\frac{x}{25}=\frac{4}{5}\)
\(\frac{x}{25}=\frac{111}{5}\)
\(x=555\)
Tìm X:
3,5 x X + 1,54 x 3,5 =15
20 + 12 : ( X - 2019 ) =32
Tính nhanh:
3/7 x 4/13 +3/7 x 9/13 + 5 và 4/7
![](https://rs.olm.vn/images/avt/0.png?1311)
1)\(3,5\cdot x+1,54\cdot3,5=15\)
\(3,5\left(x+1,54\right)=15\)
\(x+1,54=\frac{15}{3,5}\)
\(x+1,54=\frac{30}{7}\)
\(x=\frac{30}{7}-1,54\)
\(x=\frac{30}{7}-\frac{77}{50}\)
\(x=\frac{961}{350}\)
\(20+\frac{12}{x-2019}=32\)
\(\frac{12}{x-2019}=32-20\)
\(\frac{12}{x-2019}=12\)
\(x-2019=\frac{12}{12}\)
\(x-2019=1\)
\(x=1+2019\)
2)
\(\frac{3}{7}\cdot\frac{4}{13}+\frac{3}{7}\cdot\frac{9}{13}+5\frac{4}{7}\)
\(=\frac{3}{7}\cdot\frac{4}{13}+\frac{3}{7}\cdot\frac{9}{13}+13\cdot\frac{3}{7}\)
\(=\frac{3}{7}\left(\frac{4}{13}+\frac{9}{13}+13\right)\)
\(=\frac{3}{7}\cdot14\)
\(=6\)
3.5*(x-1.54)=15
x+1.54=15;3.5
x+1.54=4.28
x=4.28-1.54
x=2.74
chưa suy nghĩ
![](https://rs.olm.vn/images/avt/0.png?1311)
`(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`
![](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)
13 + x/20 = 3/4
x/20 = 3/4 - 13
x/20 = -49/4
x/20 = -245/20
=> x = -245
Hok tốt