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

bài này sai đầu bài rồi bạn ơi

-3,5 nha

x : 2 + 6 + x = 0,75

x * \(\frac{1}{2}\)+ 6 + x = 0,75

x * \(\left(\frac{1}{2}+1\right)\)+ 6 = 0,75

x *\(\frac{3}{2}\)= 0,75 - 6

x *\(\frac{3}{2}\)= -5,25

x = -5,25 : \(\frac{3}{2}\)

x = -3,5

Đ/S : 3,5

k mk nha !

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

x : 2 + x : 6 + x = 0,75

x : ( 2 + 6 + 1 ) = 0,75

x : 9 = 0,75

x = 0,75 x 9

x = 6,75

X :2 + X : 6 + X = 0,75 

X: 2 + X : 6 + X : 1 = 0,75

X: ( 2 + 6 + 1 )      = 0,75

X:     9                   = 0,75

X                         = 0,75 x 9 

X                         =    6,75

Vậy X = 6,75

mình nha !

X : 2 + X : 6 + X      = 0,75

X : 2 + X : 6 + X : 1 = 0,75

X : ( 2 + 6 + 1 )       = 0,75

X : 9                        = 0,75

X                             = 0,75 x 9

X                             = 6,75

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

\(\frac{5}{6}x+\frac{1}{2}-\frac{1}{3}x=0,75x-\frac{7}{8}\)  

\(\frac{5}{6}x-\frac{1}{3}x-0,75x=-\frac{7}{8}-\frac{1}{2}\) 

\(\frac{5}{6}x-\frac{1}{3}x-\frac{3}{4}x=-\frac{11}{8}\) 

\(\frac{1}{2}x-\frac{3}{4}x=-\frac{11}{8}\)  

\(-\frac{1}{4}x=-\frac{11}{8}\)  

\(x=-\frac{11}{8}:-\frac{1}{4}\)  

\(x=\frac{11}{2}\)  

a)

\(\begin{array}{l}\frac{2}{9}:x + \frac{5}{6} = 0,5\\\frac{2}{9}:x = \frac{1}{2} - \frac{5}{6}\\\frac{2}{9}:x = \frac{3}{6} - \frac{5}{6}\\\frac{2}{9}:x = \frac{{ - 2}}{6}\\x = \frac{2}{9}:\frac{{ - 2}}{6}\\x = \frac{2}{9}.\frac{{ - 6}}{2}\\x = \frac{{ - 2}}{3}\end{array}\)                        

Vậy \(x = \frac{{ - 2}}{3}\).

b)

\(\begin{array}{l}\frac{3}{4} - \left( {x - \frac{2}{3}} \right) = 1\frac{1}{3}\\x - \frac{2}{3} = \frac{3}{4} - 1\frac{1}{3}\\x - \frac{2}{3} = \frac{3}{4} - \frac{4}{3}\\x - \frac{2}{3} = \frac{9}{{12}} - \frac{{16}}{{12}}\\x - \frac{2}{3} = \frac{{ - 7}}{{12}}\\x = \frac{{ - 7}}{{12}} + \frac{2}{3}\\x = \frac{{ - 7}}{{12}} + \frac{8}{{12}}\\x = \frac{1}{12}\end{array}\)

Vậy\(x = \frac{1}{12}\).

c)

\(\begin{array}{l}1\frac{1}{4}:\left( {x - \frac{2}{3}} \right) = 0,75\\\frac{5}{4}:\left( {x - \frac{2}{3}} \right) = \frac{3}{4}\\x - \frac{2}{3} = \frac{5}{4}:\frac{3}{4}\\x - \frac{2}{3} = \frac{5}{4}.\frac{4}{3}\\x - \frac{2}{3} = \frac{5}{3}\\x = \frac{5}{3} + \frac{2}{3}\\x = \frac{7}{3}\end{array}\)               

Vậy \(x = \frac{7}{3}\).

d)

\(\begin{array}{l}\left( { - \frac{5}{6}x + \frac{5}{4}} \right):\frac{3}{2} = \frac{4}{3}\\ - \frac{5}{6}x + \frac{5}{4} = \frac{4}{3}.\frac{3}{2}\\ - \frac{5}{6}x + \frac{5}{4} = 2\\ - \frac{5}{6}x = 2 - \frac{5}{4}\\ - \frac{5}{6}x = \frac{8}{4} - \frac{5}{4}\\ - \frac{5}{6}x = \frac{3}{4}\\x = \frac{3}{4}:\left( { - \frac{5}{6}} \right)\\x = \frac{3}{4}.\frac{{ - 6}}{5}\\x = \frac{{ - 9}}{{10}}\end{array}\)

Vậy \(x = \frac{{ - 9}}{{10}}\).