a: \(6^{x}:3^3:4=2\)

=>\(6^{x}=2\cdot4\cdot3^3=2^3\cdot3^3=6^3\)

=>x=3

b: \(3\left(x-5\right)^3=81\)

=>\(\left(x-5\right)^3=\frac{81}{3}=27=3^3\)

=>x-5=3

=>x=3+5=8

c: \(7x-2x=6^{17}:6^{15}+3^8:2^6\)

=>\(5x=6^2+\frac{3^8}{2^6}=36+\frac{6561}{64}=\frac{8865}{64}\)

=>\(x=\frac{8865}{64}:5=\frac{1773}{64}\)

`2/3x-3/2x=5/12`

`=>-5/6x=5/12`

`=>x=-1/2`

Vậy `x=-1/2`

2/3x-3/2x=5/12

x.(2/3-3/2)=5/12

x.-5/6     =5/12

     x       =5/12:-5/6

     x       =-1/2

a)\(4\frac{2}{5}+5\frac{2}{3}+2\frac{3}{4}+\frac{3}{5}+\frac{4}{12}+\frac{1}{4}\)

\(=\left(4\frac{2}{5}+\frac{3}{5}\right)+\left(5\frac{2}{3}+\frac{4}{12}\right)+\left(2\frac{3}{4}+\frac{1}{4}\right)\)

\(=5+6+3=14\)

b)\(\frac{41}{27}\cdot\frac{13}{18}-\frac{13}{18}\cdot\frac{14}{27}\)

\(=\frac{13}{18}\cdot\left(\frac{41}{27}-\frac{14}{27}\right)\)

\(=\frac{13}{18}\cdot1=\frac{13}{18}\)

TỚ CÁM ƠN BẠN NHIỀU CHỨC BẠN HỌC GIỎI NHÉ

nhân chéo chia ngang

x= -7*36/12=-21

muốn chắc chắn thì thử lại

\(\frac{-7}{12}=\frac{21}{36}\)theo quy đồng cũng đúng

Viết lại là:

\(\frac{-7}{12}=\frac{x}{36}\)

=> \(-7.36=12.x\)

=> \(-252=12.x\)

=> \(x=\frac{-252}{12}\)

=> \(x=-21\)