Vế 2 thiếu dấu " ( " bạn ơi.

\(12\left(x+5\right)+2x=130\\\Leftrightarrow 12x+60+2x=130\\ \Leftrightarrow14x=70\\ \Leftrightarrow x=5\\ ----\\ 23\left(x-5\right)-12x=138\\ \Leftrightarrow23x-115-12x=138\\ \Leftrightarrow23x-12x=138+115\\ \Leftrightarrow11x=253\\ \Leftrightarrow x=\dfrac{253}{11}=23\\ ----\\ 360-12x+23\left(x-5\right)=278\\ \Leftrightarrow360-12x+23x-115=278\\ \Leftrightarrow-12x+23x=278+115-360\\ \Leftrightarrow11x=33\\ \Leftrightarrow x=\dfrac{33}{11}=3\)

\(6\left(x+3\right)+3\left(x-5\right)=278\\ \Leftrightarrow6x+18-3x-15=278\\ \Leftrightarrow6x-3x=278+15-18\\ \Leftrightarrow3x=275\\ \Leftrightarrow x=\dfrac{275}{3}\\ ---\\ \left(7-x\right)\left(3x-90\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}7-x=0\\3x-90=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=7\\x=30\end{matrix}\right.\)

89,6 x Y + Y : 10 + 10,3 x Y = 75,6

89,6 x Y + Y x 0,1 + 10,3 x Y = 75,6

Y x (89,6+0,1+10,3)=75,6

Y x 100 = 75,6

Y= 75,6:100

Y= 0,756

Cám ơn Dương nhé 😍

Bài 4:

\(a,2^{30}=\left(2^3\right)^{10}=8^{10};3^{20}=\left(3^2\right)^{10}=9^{10}\\ Vì:8^{10}< 9^{10}\left(Vì:8< 9\right)\Rightarrow2^{30}< 3^{20}\\ b,9^{10}.27^5=\left(3^2\right)^{10}.\left(3^3\right)^5=3^{20}.3^{15}=3^{35}\\ 243^7=\left(3^5\right)^7=3^{35}\\ Vì:3^{35}=3^{35}\Rightarrow243^7=9^{10}.27^5\)

Bài 5:

100< 5^2x-3 < 59

Đề vầy hả em?

a) 1kg = 10 hg

b) 23hg 7đag = 2370 g

c) 51 yến 73kg = 583 kg

d) 7000kg 10 tạ = 17 tấn

Các câu trên làm như POP POP

còn câu d; 7000 kg 10 tạ = 7000 kg + 10 tạ = 7 tấn + 1 tấn = 8 tấn 

38 - x.12 - x.16 = 40

38 - x.(12+16) = 40

38 - 28.x = 40

28.x = 40 - 38

28.x = 2

x= 2/28

x=1/14

100 - 50:(x-4)=75

50:(x-4)= 100 - 75

50:(x-4)=25

x-4= 50:25

x-4=2

x=2+4

x=6

6 nhaa

\(\dfrac{8}{14}\) < \(\dfrac{15}{x}\) < \(\dfrac{8}{13}\)

\(\dfrac{8\times15}{14\times15}\)  < \(\dfrac{15\times8}{x\times8}\) < \(\dfrac{8\times15}{13\times15}\)

14 \(\times\) 15 >  \(x\times\) 8 > 13 \(\times\) 15

210      > \(x\) \(\times\) 8  > 195

\(\dfrac{210}{8}\)    >  \(x\) > \(\dfrac{195}{8}\)

26,25 > \(x\) > 24,375  

Vì \(x\) là số tự nhiên nên \(x\) = 25

A          =         1 + \(\dfrac{1}{2}\) + \(\dfrac{1}{2^2}\)+......+\(\dfrac{1}{2^{99}}\)+ \(\dfrac{1}{2^{100}}\)

2A        = 2 + 1 + \(\dfrac{1}{2}\) + \(\dfrac{1}{2^2}\)+.....+ \(\dfrac{1}{2^{99}}\)

2A - A  =  2 - \(\dfrac{1}{2^{100}}\)

  A       = 2  - \(\dfrac{1}{2^{100}}\)

\(A=1+\dfrac{1}{2}+\dfrac{1}{2^2}+...+\dfrac{1}{2^{100}}\\ \Rightarrow\dfrac{1}{2}A=\dfrac{1}{2}+\dfrac{1}{2^2}+...+\dfrac{1}{2^{101}}\)

\(\Rightarrow A-\dfrac{1}{2}A=1-\dfrac{1}{2^{101}}\\ \Rightarrow\dfrac{1}{2}A=\dfrac{2^{101}-1}{2^{101}}\\ \Rightarrow A=\dfrac{2^{201}-1}{2^{100}}\)

\(\left(y:2-2\right)\left(y:3-3\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}y:2-2=0\\y:3-3=0\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}y:2=2\\y:3=3\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}y=2x2\\y=3x3\end{matrix}\right.\) \(\) \(\Rightarrow y\in\left\{4;9\right\}\)