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

= 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

\(a,6\cdot\frac{1}{3}+0,75+\frac{3}{4}:0,25\)

\(< =>6\cdot\frac{1}{3}+\frac{3}{4}+\frac{3}{4}:\frac{1}{4}\)

\(< =>2+\frac{3}{4}:\frac{1}{4}\)

\(< =>2+3\)

\(< =>5\)

\(b,19,5\cdot2,2+8,8\cdot19,5-19,5\)

\(< =>42,9+171,6-19,5\)

\(< =>214,5-19,5\)

\(< =>195\)

1) \(\left|4-2x\right|.\dfrac{1}{3}=\dfrac{1}{3}\)

\(\left|4-2x\right|=\dfrac{1}{3}:\dfrac{1}{3}\)

\(\left|4-2x\right|=\dfrac{1}{3}.3\)

\(\left|4-2x\right|=1\)

=>\(4-2x=\pm1\)

+)\(TH1:4-2x=1\) +)\(TH2:4-2x=-1\)

\(2x=4-1\) \(2x=4-\left(-1\right)\)

\(2x=3\) \(2x=4+1\)

\(x=3:2\) \(2x=5\)

\(x=1,5\) \(x=5:2\)

Vậy x=1,5 \(x=2,5\)

Vậy x=2,5

2) \(\left(-3\right)^2:\left|x+\left(-1\right)\right|=-3\)

\(9:\left|x+\left(-1\right)\right|=-3\)

\(\left|x+\left(-1\right)\right|=9:\left(-3\right)\)

\(\left|x+\left(-1\right)\right|=-3\)

=> \(x+\left(-1\right)\) sẽ không có giá trị nào ( Vì giá trị tuyệt đối luôn luôn lớn hơn hoặc bằng 0 )

Vậy x = \(\varnothing\)

3) \(\left|\dfrac{3}{2}-x\right|+\left(-\dfrac{4}{5}\right)=-\dfrac{14}{5}\)

\(\left|\dfrac{3}{2}-x\right|=\left(-\dfrac{14}{5}\right)-\left(-\dfrac{4}{5}\right)\)

\(\left|\dfrac{3}{2}-x\right|=\left(-\dfrac{14}{5}\right)+\dfrac{4}{5}\)

\(\left|\dfrac{3}{2}-x\right|=-\dfrac{10}{5}\)

\(\left|\dfrac{3}{2}-x\right|=-2\)

=> \(\dfrac{3}{2}-x\) không có giá trị nào thỏa mãn ( Vì giá trị tuyệt đối không thể là số nguyên âm )

Vậy x=\(\varnothing\)

=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`

=3/4x(0,25+1,25-0,5)=3/4x10=15/2

=136,78*1-136,78*1+136,78*1

=136,78

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, \(\dfrac{3}{5}\)\(x\) + \(\dfrac{2}{3}\) = 2\(\dfrac{2}{3}\)

     \(\dfrac{3}{5}\)\(x\) + \(\dfrac{2}{3}\) = \(\dfrac{8}{3}\)

     \(\dfrac{3}{5}\)\(x\)        = \(\dfrac{8}{3}\) - \(\dfrac{2}{3}\)

      \(\dfrac{3}{5}\)\(x\)       = 2

         \(x\)        = 2 : \(\dfrac{3}{5}\)

          \(x\)       = \(\dfrac{10}{3}\)