\(\frac{17}{8}+\frac{28}{15}-\frac{8}{15}=\frac{17}{8}+\frac{4}{3}=\frac{83}{24}=3\frac{11}{24}\)

=> chọn a

Đáp án : a) 311/24

\(\dfrac{2}{1}+\dfrac{12}{56}=\dfrac{112+12}{56}=\dfrac{122}{56}=\dfrac{61}{28}\)

\(\left(\dfrac{8+7}{15}\right):\dfrac{2}{11}\)

\(1:\)\(\dfrac{2}{11}\)

\(\dfrac{11}{2}\)

\(\dfrac{2}{1}+\dfrac{12}{56}=\dfrac{112}{56}+\dfrac{12}{56}=\dfrac{122}{56}=\dfrac{61}{28}\)

\(=\left(\dfrac{8}{15}+\dfrac{7}{15}\right)\times\dfrac{11}{2}=\dfrac{15}{15}\times\dfrac{11}{2}=1\times\dfrac{11}{2}=\dfrac{11}{2}\)

2 + 3/8 x 4/7 =61/28
8/15 : 2/11 + 7/15 : 2/11 =11/2

\(\dfrac{8}{15}:\dfrac{2}{11}-\dfrac{7}{15}:\dfrac{2}{11}\)

\(=\left(\dfrac{8}{15}-\dfrac{7}{15}\right).\dfrac{11}{2}\)

\(=\dfrac{1}{15}.\dfrac{11}{2}=\dfrac{11}{30}\)

\(=\left(\dfrac{8}{15}-\dfrac{7}{15}\right):\dfrac{2}{11}\\ =\dfrac{1\times11}{15\times2}=\dfrac{11}{30}\)

\(\left(\dfrac{8}{15}-\dfrac{7}{15}\right):\dfrac{11}{2}\)

\(\dfrac{1}{15}x\dfrac{11}{2}=\dfrac{11}{30}\)

=(8/15+7/15):2/11

=1:2/11

=11/2

\(\frac{8}{15}:\frac{2}{11}+\frac{7}{15}:\frac{2}{11}\)

\(=\frac{8}{15}\times\frac{11}{2}+\frac{7}{15}\times\frac{11}{2}\)

\(=\frac{11}{2}\times\left(\frac{8}{15}+\frac{7}{15}\right)\)

\(=\frac{11}{2}\times1\)

\(=\frac{11}{2}\)

P/s tham khảo nha

8: \(=\dfrac{-5}{9}-\dfrac{4}{9}+\dfrac{8}{15}+\dfrac{7}{15}-\dfrac{2}{11}=\dfrac{-2}{11}\)

9: =2/7-2/5+5/7=1-2/5=3/5

10: \(=\dfrac{7}{19}\left(\dfrac{8}{11}+\dfrac{3}{11}\right)-\dfrac{12}{19}=\dfrac{-5}{19}\)

11: \(=\dfrac{-5}{7}\left(\dfrac{2}{11}+\dfrac{9}{11}\right)=\dfrac{-5}{7}\)

8 = -2/11

9 = 3/5

10 = -5/19

11 = -5/7

11 = 5/13

\(\dfrac{8}{15}:\dfrac{2}{11}-\dfrac{7}{15}:\dfrac{2}{11}=\left(\dfrac{8}{15}-\dfrac{7}{15}\right):\dfrac{2}{11}=\dfrac{1}{15}:\dfrac{2}{11}=\dfrac{11}{30}\)

\(\left(\dfrac{8}{15}-\dfrac{7}{15}\right):\dfrac{2}{11}=\dfrac{1}{15}\)x\(\dfrac{11}{2}=\dfrac{11}{30}\)

\(\dfrac{8}{15}\) : \(\dfrac{2}{11}\) - \(\dfrac{7}{15}:\dfrac{2}{11}\) = \(\dfrac{11}{30}\)

cách 1 :

\(\frac{3}{5}\chi\frac{7}{9}+\frac{3}{5}\chi\frac{2}{9}\)

= \(\frac{3}{5}\chi\left(\frac{7}{9}+\frac{2}{9}\right)\)

= \(\frac{3}{5}\chi1\)

=  \(\frac{3}{5}\)

cách 2 : 

\(\frac{3}{5}\chi\frac{7}{9}+\frac{3}{5}\chi\frac{2}{9}\)

= \(\frac{7}{15}\)   +  \(\frac{2}{15}\)

=        \(\frac{9}{15}=\frac{3}{5}\)

\(C1:\frac{3}{5}.\frac{7}{9}+\frac{3}{5}.\frac{2}{9}\)                                            \(C2:\frac{3}{5}.\frac{7}{9}+\frac{3}{5}.\frac{2}{9}\)

\(=\frac{3}{5}\left(\frac{7}{9}+\frac{2}{9}\right)=\frac{3}{5}.1=\frac{3}{5}\)                     \(=\frac{7}{15}+\frac{2}{15}=\frac{3}{5}\)

\(C1:\frac{8}{15}:\frac{2}{11}+\frac{7}{15}:\frac{2}{11}\)                                      \(C2:\frac{8}{15}:\frac{2}{11}+\frac{7}{15}:\frac{2}{11}\)

\(=\left(\frac{8}{15}+\frac{7}{15}\right):\frac{2}{11}=1:\frac{2}{11}=\frac{11}{2}\)           \(=\frac{44}{15}+\frac{77}{30}=\frac{88}{30}+\frac{77}{30}=\frac{11}{2}\)

a)3/15*7/9+3/5*2/9

=(3/15*7/9)+(3/5*2/9)

=21/45+6/45

=27/45=3/5

c2:

=3/5*(7/9+2/9)

=3/5*9/9

=3/5

b)

=(8/15:2/11)+(7/15:2/11)

=44/15+77/30

=11/2

c2)

=(8/15+7/15):2/11

=15/15:2/11

=11/2

a) Cách 1:

(6/7 - 4/7):2/5

=2/7 : 2/5

=5/7

Cách 2:

(6/7 - 4/7):2/5

=6/7:2/5 - 4/7:2/5

=15/7-10/7

=5/7

b) Cách 1:

8/15:2/11+7/15:2/11

=44/15+77/30

=165/30=11/2

Cách 2:

8/15:2/11+7/15:2/11

= (8/15+7/15):2/11

=1:2/11

=11/2