17/35 nhân 9/5 nhân 4/5 

= 17/35 nhân ( 9/5 nhân 4/5 )

= 17/35 nhân 13/5

=  221/175

\(\frac{37}{35}:\frac{5}{4}:\frac{74}{25}\)

\(=\frac{37}{35}:\left(\frac{5}{4}\times\frac{74}{25}\right)\)

\(=\frac{37}{35}:\frac{37}{10}\)

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

\(\frac{37}{35}:\frac{5}{4}:\frac{74}{25}\)

=\(\frac{37}{35}x\frac{4}{5}x\frac{25}{74}\)

\(=\left(\frac{37}{35}x\frac{25}{74}\right)x\frac{4}{5}\)

\(=\frac{1}{7}x\frac{5}{2}x\frac{4}{5}\)

\(=\frac{1x5x2x2}{7x2x5}\)

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

=2/75

10 x 5 + 5 x 10

c1 : 10 x (5 + 5)

        = 10 x 10

        = 100

c2 : (10 + 10) x 5 

       = 20 x 5

       = 100

50 + 10 + 90 + 50 + 30 + 60 + 10 + 70 + 50 + 50

c1 : (50 + 50) + (10 + 90) + (30 + 60 + 10) + (50 + 50) + 70

      =  100 + 100 + 100 + 100 + 70

      =   100 x 4 + 70

      = 400 + 70

      = 470

c2: 50 x 4 + (10 + 90) + (70 + 30) + (60 + 10)

     = 200 + 100 + 100 + 70

    = 200 + 100 x 2 + 70

    = 200 + 200 + 70

    = 200 x 2 + 70

     = 400 + 70 = 470

a ) \(=\frac{35\cdot42}{5\cdot2}=\frac{7\cdot5\cdot2\cdot21}{5\cdot2}\)

\(=\frac{7\cdot21}{1}=147\)

b) \(=\frac{54\cdot35}{7\cdot9}\)

\(=\frac{6\cdot9\cdot7\cdot5}{7\cdot9}\)

\(=\frac{6\cdot5}{1}=30\)

35x42/5x2= 5x7x2x12/5x2=84

54x35/7x9=6x9x7x5/7x9=30

\(Q=\frac{5}{30}+\frac{5}{30}+\frac{5}{30}+\frac{5}{30}+\frac{5}{30}\)

\(=\frac{5}{30}.5\)

\(=\frac{5}{6}\)

5/30+15/90+25/150+35/210+45/270

=1/6+1/6+1/6+1/6+1/6

=1/30

\(\dfrac{21}{5}X\dfrac{35}{14}=\dfrac{21}{5}X\dfrac{5}{2}\)

\(\dfrac{21}{5}X\dfrac{5}{2}=\)\(\dfrac{105}{10}\)=\(\dfrac{21}{2}\)

691.01 :)