90 : xx = 6    

=> xx = 90 : 6 = 15

=> cái vế  trong ngoặc là 0.

rồi bạn làm tiếp nha

\(\dfrac{-12}{25}.\left(\dfrac{3}{4}-x+\dfrac{6}{-11}-\dfrac{5}{6}\right)=0\)

\(\dfrac{3}{4}-x+\dfrac{-6}{11}-\dfrac{5}{6}=0\)

\(\dfrac{3}{4}-x+\dfrac{-91}{66}=0\)

\(\dfrac{3}{4}-x=0-\left(\dfrac{-91}{66}\right)\)

\(\dfrac{3}{4}-x=\dfrac{91}{66}\)

\(x=\dfrac{-83}{132}\)

a: Ta có: \(-\dfrac{12}{25}\cdot\left(\dfrac{3}{4}-x+\dfrac{6}{-11}-\dfrac{5}{6}\right)=0\)

\(\Leftrightarrow x+\dfrac{83}{132}=0\)

hay \(x=-\dfrac{83}{132}\)

Xem ở đây bạn nhé! http://olm.vn/hoi-dap/question/602318.html

S= 81/10.

a. \(=\left(\dfrac{12}{15}+\dfrac{3}{15}\right)+\left(\dfrac{4}{3}+\dfrac{5}{3}\right)+\left(\dfrac{1}{4}+\dfrac{3}{4}\right)\\ =1+2+1=4\)

b. \(x\times\dfrac{3}{4}=\dfrac{1\times3\times6\times5}{6\times5\times5\times3}\\ x\times\dfrac{3}{4}=\dfrac{1}{5}\\ x=\dfrac{1}{5}:\dfrac{3}{4}\\ x=\dfrac{4}{15}\)

a.

(12/15+3/15)+(4/3+5/3)+(1/4+3/4)

=1+3+1=5

b.X x 3/4=1/5

           X=1/5:3/4

           X=4/15

\(\dfrac{x}{12}=x+\dfrac{15}{16}\)

\(\Leftrightarrow\dfrac{x}{12}=\dfrac{16x+15}{16}\)

\(\Rightarrow12\left(16x+15\right)=16x\)

\(\Leftrightarrow192x+180=16x\)

\(\Leftrightarrow176x=-180\)

\(\Leftrightarrow x=-\dfrac{45}{44}\)

Vậy \(x=-\dfrac{45}{44}\)

\(\dfrac{x}{12}=\dfrac{x+15}{16}\)

\(\Rightarrow12\left(x+15\right)=16x\)

\(\Leftrightarrow12x+180=16x\)

\(\Leftrightarrow4x=180\)

\(\Leftrightarrow x=45\)

Vậy x = 45

\(\dfrac{x}{12}=\dfrac{x+15}{16}\)

\(16x=12\left(x+15\right)\)

\(16x=12x+180\)

\(4x=180\)

\(x=45\)

\(x-\dfrac{3}{11}=\dfrac{9}{12}\Rightarrow x=\dfrac{9}{12}+\dfrac{3}{11}=\dfrac{45}{44}\)

x-3/11=9/12

x=9/12+3/11

x=45/44

x-3/11=9/12

x=9/12+3/11

x=45/44

a. (x80x - 801).12 = 0

⇔ x80 x (- 801) = 0

⇔ -64080x = 801

⇔ x = 0

(mấy câu tiếp mik ko hiểu lắm bn viết lại rõ đề rồi mik giải tiếp)