a) \(\frac{x}{27}=\frac{-2}{3,6}\Leftrightarrow x=\frac{-2.27}{3,6}=-15\)

b) \(\frac{4\frac{1}{4}}{2\frac{7}{8}}=\frac{x}{1,61}\Leftrightarrow\frac{4,25}{2,875}=\frac{x}{1,61}\Leftrightarrow x=\frac{4,25.1,61}{2,875}=2,38\)

a) \(\frac{x}{27}=-\frac{2}{3,6}\Rightarrow x=\frac{-2.27}{3,6}=-15\)

b) \(\frac{4\frac{1}{4}}{2\frac{7}{8}}=\frac{x}{1,61}\Rightarrow\frac{\frac{17}{4}}{\frac{23}{8}}=\frac{x}{1,61}\Leftrightarrow\frac{17}{4}\cdot\frac{8}{23}=\frac{x}{1,61}\)

 \(\frac{34}{23}=\frac{x}{1,61}\Rightarrow x=\frac{1,61.34}{23}=2,38\)

Lời giải:

a.

$x:27=-2:3,6=\frac{-5}{9}$

$x=27.\frac{-5}{9}=-15$

b.

$\frac{2x+1}{-27}=\frac{-3}{2x+1}$

$\Rightarrow (2x+1)^2=(-27)(-3)=81=9^2=(-9)^2$

$\Rightarrow 2x+1=9$ hoặc $2x+1=-9$

$\Rightarrow x=4$ hoặc $x=-5$

a, ta có:27:3,6=7,5

=>-2x7,5=15

vậy x cần tìm là 15

b, -0,52:x=\(-\frac{4}{7}\)

\(\frac{-13}{25}\): x=\(\frac{-4}{7}\)

x=\(\frac{-13}{25}:\frac{-4}{7}\)

x=0,91

a)\(\frac{x}{27}=\frac{-2}{3,6}\)

=>x.3,6=27.(-2)

=>x.3,6=-54

=>x=-15

b)-0,52:x=-9,36:16,38

=>-0,52:x=-4/7

=>x=0,91

c)\(\frac{4\frac{1}{4}}{2\frac{7}{8}}=\frac{x}{1,61}\)

=>\(2\frac{7}{8}.x=4\frac{1}{4}.1,61\)

=>\(2\frac{7}{8}.x=\frac{2737}{400}\)

=>x=\(\frac{119}{50}\)

a,\(\frac{x}{27}=-\frac{2}{3,6}\)

\(\Leftrightarrow x.3,6=27.-2\)

\(\Leftrightarrow x.3,6=-54\)

\(\Leftrightarrow x=-15\)

b,\(-0,52\div x=-9,36\div16,38\)

\(\Leftrightarrow-0,52\div x=-\frac{4}{7}\)

\(\Leftrightarrow x=\frac{91}{100}\)

c,\(\frac{4\frac{1}{4}}{2\frac{7}{8}}=\frac{x}{1,61}\)

\(\Leftrightarrow\frac{4,25}{2,875}=\frac{x}{1,61}\)

\(\Leftrightarrow x.2,875=4,25.1,61\)

\(\Leftrightarrow x.2,875=6,8425\)

\(\Leftrightarrow x=2,38\)

a) \(\dfrac{x}{27}=\dfrac{-2}{3,6}\)

=> x. 3,6 = 27. (-2)

=> x.3,6 = -54

x = (-54) : 3,6

x = -15

b) -0,52 : x = -9,36 : 16,38

- 0,52 : x = \(\dfrac{-4}{7}\)

x = \(\dfrac{-4}{7}\) . ( -0,52)

x = \(\dfrac{52}{175}\)

Lời giải:

a)

b)

-0,52 : x = -9,36: 16,38 => -0,52 . 16,38 = x. (-9,36) => x = -8,5176: ( -9,36) => x = 0,91

c)

a)\(\dfrac{x}{27}=\dfrac{-2}{3,6}\)

=>x.3,6=27.(-2)

=>x . 3,6=-54

=>x=-54:3.6

=>x=-54:\(\dfrac{18}{5}\)

=>x=-54.\(\dfrac{5}{18}\)

=>x=-15

b)-0,52:x=-9,36:16,38

-\(\dfrac{13}{25}:x=-\dfrac{234}{25}:\dfrac{819}{50}\)

\(-\dfrac{13}{25}:x=-\dfrac{4}{7}\)

\(x=-\dfrac{4}{7}:\left(-\dfrac{13}{25}\right)\)

x=\(\dfrac{52}{175}\)

c)\(\dfrac{4\dfrac{1}{4}}{2\dfrac{7}{8}}=\dfrac{x}{1,61}\)

\(\dfrac{\dfrac{17}{4}}{\dfrac{23}{8}}=\dfrac{x}{1,61}\)

\(\dfrac{17}{4}:\dfrac{23}{8}=\dfrac{x}{1,61}\)

\(\dfrac{17}{4}.\dfrac{8}{23}=\dfrac{x}{1,61}\)

\(\dfrac{34}{23}=\dfrac{x}{1,61}\)

=>34.1,61=x.23

rồi bạn tự tính tự làm nốt nhé

Bài 2: 

a: 

1: \(\dfrac{a}{b}=\dfrac{c}{d}\)

\(\Leftrightarrow\dfrac{a+b}{a}=\dfrac{c+d}{c}\)

hay \(\dfrac{a}{a+b}=\dfrac{c}{c+d}\)

a,x/27=-2/3,6                      b,-0,52:x=-9,36:16,38

=)) x.3,6=27.(-2)                     -0,52:x=-4/7

=)) x.3,6=-54                            x=-0,52:(-4/7)

=)) x=-15                                   x=0,91

a) \(\left(\frac{1}{3}.x\right):\frac{2}{3}=\frac{7}{4}:\frac{2}{5}\)

\(\left(\frac{1}{3}.x\right):\frac{2}{3}=\frac{35}{8}\)

\(\Rightarrow\frac{1}{3}.x=\frac{35}{8}.\frac{2}{3}\)

\(\Rightarrow\frac{1}{3}.x=\frac{35}{12}\)

\(\Rightarrow x=\frac{35}{12}:\frac{1}{3}\)

\(\Rightarrow x=\frac{35}{4}\)

Vậy \(x=\frac{35}{4}\)

a) x= \(\frac{35}{4}\)

\(a.\left(\frac{1}{3}.x\right):\frac{2}{3}=\frac{7}{4}:\frac{2}{5}\)

    \(\left(\frac{1}{3}.x\right):\frac{2}{3}=\frac{35}{8}\)

          \(\left(\frac{1}{3}.x\right)=\frac{35}{8}.\frac{2}{3}\)

          \(\left(\frac{1}{3}.x\right)=\frac{35}{12}\)

                    \(x=\frac{35}{12}:\frac{1}{3}\)

                    \(x=\frac{35}{4}\)

\(b.4,5:0,3=2,25:\left(0,1.x\right)\)

\(\Rightarrow2,25:\left(0,1.x\right)=4,5:0,3\)

     \(2,25:\left(0,1.x\right)=15\)

     \(2,25:\left(0,1.x\right)=2,25:15\)

                \(\left(0,1.x\right)=0,15\)

                          \(x=0,15:0,1\)

                          \(x=1,5\)

\(c.8:\left(\frac{1}{4}.x\right)=2:0,02\)

   \(8:\left(\frac{1}{4}.x\right)=100\)

        \(\left(\frac{1}{4}.x\right)=8:100\)

        \(\left(\frac{1}{4}.x\right)=\frac{2}{25}\)

                  \(x=\frac{2}{25}:\frac{1}{4}\)

                  \(x=\frac{8}{25}\)

\(d.3:\frac{9}{4}=\frac{3}{4}:\left(6.x\right)\)

\(\Rightarrow\frac{3}{4}:\left(6.x\right)=3:\frac{9}{4}\)

     \(\frac{3}{4}:\left(6.x\right)=\frac{4}{3}\)

           \(\left(6.x\right)=\frac{3}{4}:\frac{4}{3}\)

          \(\left(6.x\right)=\frac{9}{16}\)

                \(x=\frac{9}{16}:6\)

                \(x=\frac{3}{32}\)

 ^...^ ^_^