a: \(\Leftrightarrow\dfrac{x}{-4}=\dfrac{21}{y}=\dfrac{z}{-80}=\dfrac{3}{4}\)

=>x=-3; y=28; z=-60

b: 5/12=x/-72

=>x=-72*5/12=-6*5=-30

c: =>x+3=-5

=>x=-8

a) \(x+15=18-\left(-27\right)\)

\(\Leftrightarrow x+15=18+27\)

\(\Leftrightarrow x+15=45\)

\(\Leftrightarrow x=45-15\)

\(\Leftrightarrow x=30\)

b) \(-x+7=28\)

\(\Leftrightarrow-x=28-7\)

\(\Leftrightarrow-x=21\)

\(\Leftrightarrow x=-21\)

c) \(20-\left(-x\right)=14\)

\(\Leftrightarrow20+x=14\)

\(\Leftrightarrow x=14-20\)

\(\Leftrightarrow x=-6\)

d) \(2x+5=x-14\)

\(\Leftrightarrow2x+5-\left(x-14\right)=0\)

\(\Leftrightarrow2x+5-x+14=0\)

\(\Leftrightarrow x+19=0\)

\(\Leftrightarrow x=0-19\)

\(\Leftrightarrow x=-19\)

e) \(x+17=-8-20\)

\(\Leftrightarrow x+17=-\left(8+20\right)\)

\(\Leftrightarrow x+17=-28\)

\(\Leftrightarrow x=-28-17\)

\(\Leftrightarrow x=-\left(28+17\right)\)

\(\Leftrightarrow x=-45\)

f) \(3x+15=2x+6\)

\(\Leftrightarrow3x+15-\left(2x+6\right)=0\)

\(\Leftrightarrow3x+15-2x-6=0\)

\(\Leftrightarrow x+9=0\)

\(\Leftrightarrow x=0-9\)

\(\Leftrightarrow x=-9\)

2,

a.\(\left|a+3\right|=\left|-5\right|\)

\(a+3=5\)

\(a=2\)

Vậy a=2

b.\(\left|a-1\right|=2+\left|-3\right|\)

\(a-1=2+3\)

\(a-1=5\)

\(a=6\)

Vậy a=6

a) x-6= -15

=>x   =-15 + 6

=>x   =-9

b) 14-(5-x)=-27+4

=>14-5+x=-23

=>9+x    = -23

=>x         =-23-9

=>x         =-32

???????????????????????

a)\(x+\frac{15}{16}+\frac{7}{8}=\frac{15}{4}\)

\(x+\frac{29}{16}=\frac{15}{4}\)

\(x=\frac{15}{4}-\frac{29}{16}\)

\(x=\frac{31}{16}\)

b)\(x-\frac{27}{28}-\frac{9}{14}=\frac{13}{7}\)

\(x-\frac{45}{28}=\frac{13}{7}\)

\(x=\frac{13}{7}+\frac{45}{28}\)

\(x=\frac{97}{28}\)

c)\(x\times\frac{1}{5}+x+\frac{1}{6}=\frac{2}{3}\)

\(x\times\frac{1}{5}+x=\frac{2}{3}-\frac{1}{6}\)

\(x\times\left(\frac{1}{5}+1\right)=\frac{1}{2}\)

\(x\times\frac{6}{5}=\frac{1}{2}\)

\(x=\frac{1}{2}:\frac{6}{5}\)

\(x=\frac{5}{12}\)

d)\(x:14=\frac{1}{4}+\frac{2}{9}+\frac{3}{4}\)

\(x:14=\frac{11}{9}\)

\(x=\frac{11}{9}\times14\)

\(x=\frac{154}{9}\)

#H

a. x = 9

b. x = 5

c. x = 8

Đề nhìn vô lí quá

a. x = 9

b. x = 5

c. x = 8

Tham hkaor

a. x = 9

b. x = 5

c. x = 8

Đề nhìn vô lí quá

\(a,2.\left(x-5\right)-3.\left(x+7\right)=14\)

            \(2x-10-3x-21=14\)

                                 \(-x-31=14\)

                                                \(x=-31-14\)

                                                \(x=-45\)

\(b,5.\left(x-6\right)-2\left(x+3\right)=12\)

             \(5x-30-2x-6=12\)

                                \(3x-36=12\)

                                           \(3x=12+36\)

                                           \(3x=48\)

                                              \(x=16\)

\(c,-5.\left(2-x\right)+4.\left(x-3\right)=10.x-15\)

              \(-10+5x+4x-12=10x-15\)

                                    \(-6x-22=10x-15\)

                                  \(-6x-10x=-15+22\)

                                             \(-16x=7\)

                                                      \(x=-\frac{7}{16}\)

Câu d , e f tương tự nha

bạn làm rất   đúng ,cảm ơn bn nhìu

dễ mà bn

Bài 6:

a)\(\left(-18\right)-\left(-3\right)-12\)

\(=\left(-18\right)+3-12\)

\(=-15-12\)

\(=-27\)

b)\(85.\left(35-27\right)-35.\left(85-27\right)\)

\(=85.35-85.27-35.85+35.27\)

\(=85.\left(35-27-35\right)+35.27\)

\(=85.\left(-27\right)+35.27\)

\(=27.\left(-85+35\right)\)

\(=27.\left(-50\right)\)

\(=-1350\)

c)\(\left(-45\right).69+31.\left(-45\right)\)

\(=\left(-45\right).\left(69+31\right)\)

\(=\left(-45\right).100\)

\(=-4500\)

Bài 7:

a)\(\left(2-x\right)+10=-14\)

\(\Rightarrow2-x=-24\)

\(\Rightarrow x=26\)

b)\(14.\left|x\right|=28\)

\(\Rightarrow\left|x\right|=2\)

\(\Rightarrow\orbr{\begin{cases}x=2\\x=-2\end{cases}}\)

c)\(31-\left(17+x\right)=55\)

\(\Rightarrow17+x=-24\)

\(\Rightarrow x=-41\)

(-18)-(-3)-12=-27

85.(35-27)-35.(85-27)=-1350

(-45).69+31.(-45)=-4500

(2-x)+10=-14

\(\Leftrightarrow\)(2-x)=-14-10

\(\Leftrightarrow\)2-x=-24

\(\Rightarrow\)x=2-(-24)

\(\Rightarrow\)x=26

14.lxl=28

\(\Leftrightarrow\)lxl=28:14

\(\Leftrightarrow\)lxl=2

\(\Rightarrow\)x=-2