Bài 1:a, 7,24.x+2,76.x=35

<=>x(7,24+2,76)=35

<=>10x=35

<=>x=3,5

b,3/4-(x+1/7)=6-11/2

<=>3/4-(x+1/7)=1/2

<=>x+1/7=3/4-1/2

<=>x=3/28

Bài 2:

Để 2x1y chia hết cho 5 thì y=0;5; 2+x+1+y chia hết cho 3 (0<x;y<10)

Khi y=0

Suy ra x=0;3;6;9

Khi y=5 \

suy ra x=1;4;7

a) 7,24 x X + 2,76 x X = 35

   (7,24 + 2,76) x X     = 35

           10        x X     = 35

                         X     = 35 : 10

                         X     =    3,5

b) \(\frac{3}{4}\) - \(\left(x+\frac{1}{7}\right)\) = 6 - \(\frac{11}{2}\)

    \(\frac{3}{4}\) - X + \(\frac{1}{7}\)          =   \(\frac{1}{2}\)

    \(\frac{3}{4}\) - X                  = \(\frac{1}{2}\) - \(\frac{1}{7}\)

    \(\frac{3}{4}\) - X                  =     \(\frac{5}{14}\)

           X                  = \(\frac{3}{4}\) - \(\frac{5}{14}\)

           X                  =     \(\frac{11}{28}\)

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=\(\varnothing\)

a: \(0.4\cdot\sqrt{0.25-\sqrt{\dfrac{1}{4}}}=0.4\cdot\sqrt{0.25-0.5}\)(đề này sai rồi bạn)

b: \(\dfrac{3}{2}+2\left(x-1\right)=-5\dfrac{1}{2}\)

\(\Leftrightarrow2\left(x-1\right)=\dfrac{-11}{2}-\dfrac{3}{2}=-7\)

\(\Leftrightarrow x-1=\dfrac{-7}{2}\)

hay \(x=-\dfrac{5}{2}\)

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,=11/12 x 8/15 - 1/6:2

  = 22/45-1/2

  = 73/180

b, =9/4:0.01 

   = 225

K nha

0,25 x 40

= 10

....

Cái chỗ phần b là ( 2 và 1/4 - 0,25 ) :0,01 phần 0,25x 40 nhé mn

a)\(x-\frac{1}{4}=\frac{5}{8}\)

\(x=\frac{5}{8}+\frac{1}{4}\)

\(x=\frac{7}{8}\)

b)\(\frac{x}{12}=\frac{-1}{24}-\frac{1}{8}\)

\(\frac{x}{12}=\frac{-1}{24}+\frac{-1}{8}\)

\(\frac{x}{12}=\frac{-1}{6}\)

\(x=\frac{-1}{6}\times12\)

\(x=-2\)

a)x-1/4=5/8

=>x=5/8+1/4

x=7/8

b) x/12=-1/24-1/8

=>x/12=-1/6

=>x=-2

c).......... Tự làm

c)

\(\left(\frac{1}{4}-\frac{3}{10}x\right)\times\frac{1}{3}=\frac{-51}{6}+\frac{1}{4}\)

\(\left(\frac{1}{4}-\frac{3}{10}x\right)\times\frac{1}{3}=\frac{-33}{4}\)

\(\frac{1}{4}-\frac{3}{10}x=\frac{-33}{4}\div\frac{1}{3}\)

\(\frac{1}{4}-\frac{3}{10}x=\frac{-33}{4}\times3\)

\(\frac{1}{4}-\frac{3}{10}x=\frac{-99}{4}\)

\(\frac{3}{10}x=\frac{1}{4}-\left(\frac{-99}{4}\right)\)

\(\frac{3}{10}x=\frac{1}{4}+\frac{99}{4}\)

\(\frac{3}{10}x=25\)

\(x=\frac{250}{3}\)