yx1/2+y-yx7/2=21-yx1/4 =>yx1/2+y-yx7/2+yx1/4=21

=>y x (1/2+1-7/2+1/4)=21 => y x (-7/4)=21 =>y=21:(-7/4)=21 x (4/-7)=-12

\(\frac{2}{3}\times\frac{1}{5}+\frac{3}{10}\times\frac{2}{3}+\frac{4}{6}\times\frac{1}{2}\)

\(=\frac{2}{3}\times\frac{1}{5}+\frac{3}{10}\times\frac{2}{3}+\frac{2}{3}\times\frac{1}{2}\)

\(=\frac{2}{3}\times\left(\frac{1}{5}+\frac{3}{10}+\frac{1}{2}\right)\)

\(=\frac{2}{3}\times\frac{10}{10}\)

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

2/3 x 1/6 x 9/11 

= 1/9 x 9/11

= 1/11

1/11 nhé bn tk mk nhé mk sẽ kb

(2/3x1/6)x9/11

= 1/9x9/11

=1/11

X × 2 + X × 3 + X × 4 + X = 2130. 

= X × 2 + X × 3 + X × 4 + X × 1 = 2130

= X × ( 2 +  3 + 4 + 1 ) = 2130

 = X × 10 = 2130

X              = 2130 : 10

X              = 213

HT NHA

2/3 +5/9 - 3/4 =17/36

2/7 :2/3 -1/7 = 2/7

2/5 * 1/4 :3/8 = 4/15 nha bạn

=17/36

=1/2

=4/15

nhớ tk cho mình nhé

2/3+5/9-3/4=6/9+5/9-3/4=11/8-3/4=11/8-6/8=5/8                                                                                                                                                                                                                                                                                                                                            2/7:2/3-1/7=2/7x3/2-1/7=6/14-1/7=6/14-2/14=4/14                                                                                                                                                                                                                                                                                                                                        2/5x1/4:3/8=2/20x8/3=16/60=4/15

17/16

2/7

4/15

mk nha

2/3 + 5/9 - 3/4

= 11/9 - 3/4

= 17/36

2/7 : 2/3 - 1/7

= 2/7 x 3/2 - 1/7

= 3/7 - 1/7

= 1/2

2/5 x 1/4 : 3/8

= 1/10 : 3/8

= 1/10 x 8/3

= 4/15

2 - 5/7 + 9/21 = 12/7

5/8 : 3 x 24/25 = 1/5

k minh di

2 - \(\frac{5}{7}\)+\(\frac{9}{21}\)= \(\frac{9}{7}\)+\(\frac{9}{21}\)= \(\frac{12}{7}\)

\(\frac{5}{8}\): 3 x\(\frac{24}{25}\)= \(\frac{5}{24}\)x \(\frac{24}{25}\)= \(\frac{1}{5}\)

mk nhanh nhất tk mk nha

2/3×3/4×4/5÷1/5=2

2/5×3/4×5/6÷3/4=0.33333333333......

2/3 x 3/4 x 4/5 : 1/5 = 6/12 x 4/5 :1/5 = 24/60 :1/5 = 4/10 : 1/5 = 4/10 x 5/1 = 20/10 = 2

2/5 x 3/4 x 5/6 : 3/4 = 6/20 x 5/6 : 3/4 = 3/10 x 5/6  : 3/4 = 15/60 : 3/4 = 1/4 : 3/4 = 1/4 x 4/3 = 4/12 = 1/3

k cho mk nha!

\(\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\div\frac{1}{5}\)

\(=\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times\frac{5}{1}\)

\(=\frac{2\times3\times4\times5}{3\times4\times5\times1}\)

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

\(=2\)

a; 60 \(\times\) (\(\dfrac{7}{12}\) + \(\dfrac{4}{15}\))

= 60 \(\times\) \(\dfrac{7}{12}\) + 60 \(\times\) \(\dfrac{4}{15}\)

= 35 + 16

= 51