78x17-7x87=6177

78 x 17 - 7x 87 = 1326 - 609

                       =    717

. là dấu nhân
\(58.75+58.50.25\)
\(=58.75+58.1250\)
\(=58.\left(75+1250\right)\)
\(=58.1325=76850\)

Các bạn giúp mình với mình đang cần gấp lắm

\(\frac{7}{3}.9-\frac{9}{4}.5+\frac{11}{5}.6-\frac{13}{6}.7+\frac{15}{7}.8-\frac{17}{8}.9+\frac{19}{9}.10\)

\(=21-\frac{45}{4}+\frac{66}{5}-\frac{91}{6}+\frac{120}{7}-\frac{153}{8}+\frac{190}{9}\)

\(=26,91230159\)

Lớp mấy đó

minh chon B k di

BT B k minh nha nhanh nhat do

Ket qua la bt C 

Giúpppp mìnhh vớiiiiiiiiiiiiiiiiiiiiiiiii nhanhhhhhhhhhhh lênnnnnnnnnnnnnnnnn

Nhanh rồi mình tích cho

a: \(\dfrac{6}{7}\cdot\dfrac{16}{15}\cdot\dfrac{7}{6}\cdot\dfrac{21}{32}=\dfrac{16}{32}\cdot\dfrac{21}{15}=\dfrac{1}{2}\cdot\dfrac{7}{5}=\dfrac{7}{10}\)

b: \(\dfrac{21}{17}\cdot\dfrac{13}{14}\cdot56\cdot\dfrac{3}{42}=\dfrac{21}{14}\cdot\dfrac{13}{17}\cdot\dfrac{1}{14}\cdot56=\dfrac{78}{17}\)

c: \(=\dfrac{11}{21}\left(\dfrac{7}{4}+\dfrac{5}{4}\right)=\dfrac{11}{21}\cdot3=\dfrac{11}{7}\)

87 . 23 + 13 . 93 + 70 . 87

= 87 . 23 + 70 . 87 + 13 . 93

= 87 . (23 + 70) + 13 . 93

= 87 . 93 + 13 . 93

= 93 . (87 + 13)

= 93 . 100

= 9300.

87*23+13*93+70*87

=87.23+70.87+13.93

=87.(23+70)+13.93

=87.93+13.93

=93.(87+13)

=93.100

=9300

hello

\(13.(-78)+78.(-87)\)

\(=-1014+78.(-87)\)

\(=-1014+(-6786)\)

\(=-7800\)

\(13 . \left(-78\right)+78 . \left(-87\right)=\left[13+\left(-87\right)\right] . \left[\left(-78\right)+78\right]=-74 . 0=0\)

\(13.\left(-78\right)+78.\left(-87\right)\)

\(=13.\left(-78\right)+87.\left(-78\right)\)

\(=-78\left(13+87\right)\)

\(=-78.100\)

\(=-7800\)