1) 2,75 - 5/6 × 2/5 = 2,75 - (5/6) × (2/5) = 2,75 - 1/3 = 2,75 - 0,33 = 2,42

2) 1,25 - (5/6 - 0,75) - 3/5 = 1,25 - (5/6 - 0,75) - 3/5 = 1,25 - (5/6 - 3/4) - 3/5 = 1,25 - (5/6 - 9/12) - 3/5 = 1,25 - (10/12 - 9/12) - 3/5 = 1,25 - 1/12 - 3/5 = 1,25 - 0,08 - 0,6 = 1,25 - 0,68 = 0,57

3) 4/9 × 0,75 + 8/5 + 3,125 = (4/9) × 0,75 + 8/5 + 3,125 = 0,44 + 8/5 + 3,125 = 0,44 + 1,6 + 3,125 = 0,44 + 4,725 = 5,165

4) 1,125 - 4/7 - 0,12 = 1,125 - (4/7) - 0,12 = 1,125 - 0,57 - 0,12 = 0,435 - 0,12 = 0,315

5) (1/3 + 0,4) × 3,5 + (1/6 + 0,75) × 6/5

a)  \(0,75\times26+49\times\frac{3}{4}+\frac{3}{4}\times24+\) \(0,75\)

    \(=\) \(0,75\times\left(26+1\right)+\frac{3}{4}\times\left(49+24\right)\)

     \(=\)  \(\frac{3}{4}\times27+\frac{3}{4}\times73\)

      \(=\) \(\frac{3}{4}\times\left(27+73\right)\)

        \(=\)\(\frac{3}{4}\times100=75\)

b) câu b,c làm tương tự

= 0,75 x 0,25 + 0,75 x 1,25 - 0,75 x 0,5

= 0,75 x ( 0,25 + 1,25 - 0,5 )

= 0,75 x 1

= 0,75

0.75

1, (0,25 - \(x\)) : - \(\dfrac{3}{5}\) = - \(\dfrac{3}{4}\)

    0,25 - \(x\)           = - \(\dfrac{3}{4}\) x (- \(\dfrac{3}{5}\))

     0,25 - \(x\)           = \(\dfrac{9}{20}\)

                \(x\)          = 0,25 - 0,45 

                \(x\)          = - 0,2 

2, - \(\dfrac{3}{8}\)\(x\) - 0,75 = - 1\(\dfrac{1}{2}\)

    - \(\dfrac{3}{8}\)\(x\) - 0,75  = -1,5

       \(\dfrac{3}{8}\)\(x\)             = - 0,75 + 1,5

       \(\dfrac{3}{8}\)\(x\)            =  0,75

          \(x\)            = 0,75 : \(\dfrac{3}{8}\)

          \(x\)           =   2

=3/4.0,25+3/4.1,25-3/4.0,5

=3/4.(0,25+1,25-0,5)

=3/4.10

=15/2

`3/4.0,25+3/4.1,25-3/4.0,5`

`=3/4.(0,25+1,25-0,5)`

`=3/4xx10=15/2`

câu 1 đáp án bằng 6 / 7,câu 2 đáp án bằng 1

a: \(\left(\dfrac{3}{4}x+2\dfrac{1}{2}\right)\cdot\dfrac{-2}{3}=\dfrac{1}{8}\)

=>\(\left(\dfrac{3}{4}x+\dfrac{5}{2}\right)=\dfrac{1}{8}:\dfrac{-2}{3}=\dfrac{-3}{16}\)

=>\(\dfrac{3}{4}x=-\dfrac{3}{16}-\dfrac{5}{2}=-\dfrac{3}{16}-\dfrac{40}{16}=-\dfrac{43}{16}\)

=>\(x=-\dfrac{43}{16}:\dfrac{3}{4}=\dfrac{-43}{16}\cdot\dfrac{4}{3}=\dfrac{-43}{12}\)

b: \(\dfrac{1}{3}\cdot x-0,5x=0,75\)

=>\(x\left(\dfrac{1}{3}-\dfrac{1}{2}\right)=0,75\)

=>\(x\cdot\dfrac{-1}{6}=0,75\)

=>\(x=-0,75\cdot6=-4,5\)

Lời giải:

$\frac{1}{4}-3x+\frac{3}{2}=-0,75$

$3x=\frac{1}{4}+\frac{3}{2}-(-0,75)=2,5$

$\Rightarrow x=2,5:3=\frac{5}{6}$

a) Ta có: \(x-\frac{2}{3}=0,75\)

\(\Leftrightarrow x-\frac{2}{3}=\frac{3}{4}\)

hay \(x=\frac{3}{4}+\frac{2}{3}=\frac{17}{12}\)

Vậy: \(x=\frac{17}{12}\)

b) Ta có: \(\frac{1}{3}+\frac{2}{3}x=-1\)

\(\Leftrightarrow\frac{2}{3}x=-1-\frac{1}{3}=-\frac{4}{3}\)

hay \(x=\frac{-4}{3}:\frac{2}{3}=\frac{-4}{3}\cdot\frac{3}{2}=-2\)

Vậy: x=-2

c) Ta có: \(\left|2x-3\right|-\frac{3}{4}=4,25\)

\(\Leftrightarrow\left|2x-3\right|=\frac{17}{4}+\frac{3}{4}=5\)

\(\Leftrightarrow\left[{}\begin{matrix}2x-3=5\\2x-3=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=8\\2x=-2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\\x=-1\end{matrix}\right.\)

Vậy: x∈{-1;4}

a, \(x-\frac{2}{3}=0.75\)

\(x=0.75-\frac{2}{3}\)

\(x=\frac{1}{12}\)

Vậy...

b, \(\frac{1}{3}+\frac{2}{3}\cdot x=-1\)

\(\frac{2}{3}\cdot x=-1-\frac{1}{3}=-\frac{4}{3}\)

\(x=-\frac{4}{3}:\frac{2}{3}=-2\)

Vậy x = -2

c, \(|2x-3|-\frac{3}{4}=4.25\)

\(|2x-3|=4.25-\frac{3}{4}=\frac{7}{2}\)

=> \(2x-3=\frac{7}{2}hay2x-3=-\frac{7}{2}\)

2x = \(\frac{7}{2}+3\) 2x = \(-\frac{7}{2}+3\)

2x = \(\frac{13}{2}\) 2x = \(-\frac{1}{2}\)

x = \(\frac{12}{2}:2=\frac{13}{4}\) x = \(-\frac{1}{2}:2\) = \(-\frac{1}{4}\)

Vậy...