a) Ap dụng tích chất dãy tỉ số = nhau

Ta có:x/2=y/3=x+y/5+7=15/15=1

x/2=1=> x=2

y/3=1=> y=3

x + x : 0,2 = 1,35
x * 1 + x * 5 = 1,35
x * ( 1 + 5 ) = 1,35
x * 6 = 1,35
x = 1,35 : 6
x = 0,225

hok tốt nha ^_^

\(\frac{x}{2}=\frac{y}{3}\)

Áp dung tính chất của dãy tỉ số bằng nhau ta có'

\(\frac{x}{2}=\frac{y}{3}=\frac{x+y}{2+3}=\frac{15}{5}=3\)

=>

x = 3 .2=6

y =3.3 =9

a.2/3 + 1/3 - x= 3/5

=> 1-x = 3/5

=>  x = 1-3/5= 2/5

b. 1/8/15 - 2/3x = 0,2

=> 2/3x= 23/15 - 1/5= 4/3

=> x= 4/3 : 2/3=2

c. 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) 2/3 + 1/3 - x = 3/5

=> 1 - x = 3/5

=> x = 1 - 3/5

     x = 2/5

b) \(1\frac{8}{15}-\frac{2}{3}x=0,2\)

=> 23/15 - 2/3x = 0,2

=> 2/3x = 23/15 - 0,2

    2/3x = 1,333333333

=>x = 1,333333333 : 2/3

    x = 2

c) ???

a, \(\frac{3}{5}\left(2x-\frac{1}{3}\right)+\frac{4}{15}=\frac{12}{30}\)

\(\Leftrightarrow\frac{3}{5}\left(2x-\frac{1}{3}\right)=\frac{2}{15}\)

\(\Leftrightarrow2x-\frac{1}{3}=\frac{2}{9}\)

\(\Leftrightarrow2x=\frac{5}{9}\)

\(\Leftrightarrow x=\frac{5}{18}\)

b,\(\left(-0,2\right)^x=\frac{1}{25}\)

\(\Leftrightarrow\left(\frac{-1}{5}\right)^x=\left(\frac{-1}{5}\right)^2\)

\(\Leftrightarrow x=2\)

c,\(\left|x-1\right|-\frac{3}{12}=\left(-\frac{1}{2}\right)^2\)

\(\Leftrightarrow\left|x-1\right|-\frac{3}{12}=\frac{1}{4}\)

\(\Leftrightarrow\left|x-1\right|=\frac{1}{2}\)

\(\Leftrightarrow\orbr{\begin{cases}x-1=\frac{1}{2}\\x-1=-\frac{1}{2}\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=\frac{3}{2}\\x=\frac{1}{2}\end{cases}}\)

\(a,\frac{3}{5}\left(2x-\frac{1}{3}\right)=\frac{12}{30}-\frac{4}{15}\)

\(\frac{3}{5}\left(2x-\frac{1}{3}\right)=\frac{2}{15}\)

\(2x-\frac{1}{3}=\frac{2}{9}\)

\(x=\frac{5}{18}\)

\(b,\left(-0,2\right)^x=\frac{1}{25}\)

\(\left(-0,2\right)^x=\left(-\frac{1}{5}\right)^2\)

\(\left(-0,2\right)^x=\left(-0,2\right)^2\)

\(x=2\)

c,/x-1/=1/2 

Nếu 
\(x-1\ge0\)

\(x\ge1\)

suy ra x-1=1/2

         x=3/2(thỏa mãn điều kiện )

nếu \(x-1\le0\)

   \(x\le1\)

suy ra x-1=-1/2

           x=1/2 (thỏa mãn điều kiện )

Vậy ...

nha !!!

Thank !

2/5.x:7/3.1/8=25/15

2/5.x:7/24=5/3

2/5.x=5/3.7/24

2/5.x=6/34

x=6/34:2/5

x=15/34

\(\frac{2}{5}x:\frac{7}{3}.\frac{1}{8}=\frac{25}{15}\Leftrightarrow\frac{2}{5}x:\frac{7}{3}.\frac{1}{8}=\frac{5}{3}\Leftrightarrow\frac{2}{5}x:\frac{7}{3}=\frac{5}{3}:\frac{1}{8}\Leftrightarrow\frac{2}{5}x:\frac{7}{3}=\frac{5}{3}.8\Leftrightarrow\frac{2}{5}x:\frac{7}{3}=\frac{40}{3}\)

\(\Leftrightarrow\frac{2}{5}x=\frac{40}{3}.\frac{7}{3}\Leftrightarrow\frac{2}{5}x=\frac{280}{3}\Leftrightarrow x=\frac{280}{3}:\frac{2}{5}\Leftrightarrow x=\frac{280}{3}.\frac{5}{2}\Leftrightarrow x=\frac{700}{3}\)

Vậy .........

\(x\times\frac{6}{25}=\frac{15}{-13}\)

x=\(\frac{15}{-13}\div\frac{6}{25}\)

x=\(-\frac{125}{26}\)

các câu còn lại làm tương tự nha!!!

\(1.x.\frac{6}{25}=\frac{15}{-13}\\ x=\frac{15}{-13}:\frac{6}{25}\\ x=-\frac{125}{26}\)

\(2.x:\frac{4}{10}=\frac{13}{-45}+\frac{8}{15}\\ x:\frac{4}{10}=\frac{11}{45}\\ x=\frac{11}{45}.\frac{4}{10}\\ x=\frac{22}{225}\)

\(3.\frac{3}{8}-\frac{1}{6}.x=\frac{1}{4}\\ \frac{1}{6}.x=\frac{3}{8}-\frac{1}{4}\\ \frac{1}{6}.x=\frac{1}{8}\\ x=\frac{1}{8}:\frac{1}{6}\\ x=\frac{3}{4}\)

\(4.\frac{1}{3}+\frac{1}{2}:x=-4\\ \frac{1}{2}:x=-4-\frac{1}{3}=-\frac{13}{3}\\ x=\frac{1}{2}:\left(-\frac{13}{3}\right)=-\frac{3}{26}\)

\(5.x+\frac{7}{12}=\frac{17}{18}-\frac{1}{9}=\frac{5}{6}\\ x=\frac{5}{6}-\frac{7}{12}\\ x=\frac{1}{4}\)

1) 3

2) 1

b) 10/57

a)

\(\Rightarrow\left(\frac{305}{2}-\frac{1187}{8}\right):\frac{1}{5}=x:\frac{3}{10}\)

\(\Rightarrow\frac{33}{8}.5=x:\frac{3}{10}\)

\(\Rightarrow x=\frac{33}{8}.5.\frac{3}{10}\)

\(\Rightarrow x=\frac{99}{16}\)