\(\dfrac{2}{3}\)x\(\dfrac{7}{4}\):\(\dfrac{a}{12}\)=\(\dfrac{2}{3}\)

=>\(\dfrac{7}{6}\):\(\dfrac{a}{12}\)=\(\dfrac{2}{3}\)

=>\(\dfrac{a}{12}\)=\(\dfrac{7}{6}\):\(\dfrac{2}{3}\)=\(\dfrac{21}{12}\)

=>a=21.

cô Nguyễn Thị Thương Hoài ơi, chỉ e bài này đi

\(\dfrac{2}{3}x\dfrac{7}{4}:\dfrac{a}{12}=\dfrac{2}{3}\)\(=>\dfrac{7}{4}:\dfrac{a}{12}=\dfrac{2}{3}\)\(=>\dfrac{a}{12}=\dfrac{7}{6}:\dfrac{2}{3}=\dfrac{21}{12}\)

`5/39xx(7 4/5xx1 2/3+8 1/3xx7 4/5)`

`=5/39xx(39/5xx5/3+25/3xx39/5)`

`=5/39xx39/5(5/3+25/3)`

`=1xx30/3`

`=10`

10

10

a=\(1\times3+\dfrac{2}{3}\times7+\dfrac{3}{7}\times13+\dfrac{4}{13}\times21+\dfrac{5}{12}\times21\)

=3+\(\dfrac{14}{3}\)+\(\dfrac{39}{7}\)+\(\dfrac{84}{13}\)+5=8+\(\dfrac{215}{21}\)+\(\dfrac{84}{13}\)=\(\dfrac{4559}{273}\)+8=\(\dfrac{6743}{273}\)

=(5/12+7/12)*2/3+1/3

=1*2/3+1/3

=2/3+1/3

=1

5/12 x 2/3 + 2/3 x 7/12 + 1/3

= 2/3 x ( 5/12 + 7/12 ) + 1/3

= 2/3 x 1 + 1/3

= 2/3 + 1/3

= 1

5/12x2/3+2/3x7/12+1/3

=2/3x(5/12+7/12)+1/3

=2/3x1+1/3

=2/3+1/3

=1

k tui nha @@@

\(\frac{5}{12}\)x \(\frac{2}{3}\)+ \(\frac{2}{3}\)x \(\frac{7}{12}\)+ \(\frac{1}{3}\)

= \(\frac{2}{3}\)x ( \(\frac{5}{12}\)+ \(\frac{7}{12}\) ) + \(\frac{1}{3}\)

= \(\frac{2}{3}\)x 1 + \(\frac{1}{3}\)

= \(\frac{2}{3}\)+ \(\frac{1}{3}\)

= 1

2/3x(5/12+7/12)+1/3

2/3x       1        +1/3

2/3+1/3

=1              k mik nhaaaaa

5/12×2/3+2/3×7/12+1/3

=2/3×(5/12+7/12)+1/3

=2/3×          1          +1/3

=              2/3           +1/3

=                       1

\(\frac{5}{12}.\frac{2}{3}+\frac{2}{3}.\frac{7}{12}+\frac{1}{3}\)

\(=\frac{2}{3}.\left(\frac{5}{12}+\frac{7}{12}\right)+\frac{1}{3}\)

\(=\frac{2}{3}.\frac{12}{12}+\frac{1}{3}\)

\(=\frac{2}{3}.1+\frac{1}{3}\)

\(=\frac{2}{3}+\frac{1}{3}\)

\(=\frac{3}{3}=1\)

Dấu "." bằng dấu x

a. = 125 + 170 + 1100 - 125 - 864 - 36 = 370

b. = 7² ( 7 + 3 ) + 5² ( 9 + 1 ) 

   = 49 x 10 + 25 x 10

   = 10 ( 49+25)

   = 10 x 74 = 740

a.125+170+1100+(-125)+(-864)+(-36)

=1395+(-125)+(-864)+(-36)

=370

b.[(7³+3.7²)+(3².5²+5²)

=(343+3.49)+(9.25+25)

=(343+147)+(225+25)

=490+250

=740

nhầm:

5/12x2/3+2/3x7/12++1/3

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