3/5 x 5 + 12 x 3/5 + 3 : 5/3

=3/5 x 5 + 12 x 3/5 + 3 x 3/5

= 3/5 x ( 5 + 12 + 3 ) 

= 3/5 x 20

= 12

a)\(\frac{1}{2}:\frac{1}{5}+\frac{1}{3}:\frac{1}{5}+\frac{1}{6}:\frac{1}{5}\)

=\(\left(\frac{1}{2}+\frac{1}{3}+\frac{1}{6}\right):\frac{1}{5}\)

=\(1:\frac{1}{5}\)

=5

b)\(\frac{1515\text{×}161616}{151515\text{×}1616}\)

=1

\(\frac{5}{5}x\)\(\frac{17}{21}+\frac{17}{21}x\)\(\frac{2}{5}\)

=(\(\frac{5}{5}+\frac{2}{5}\)) x\(\frac{17}{21}\)

=\(\frac{7}{5}x\)\(\frac{17}{21}\)

\(\frac{119}{105}\)

ko hiểu

 7/5x17/21=17/15 mới đúng

\(\frac{5}{9}\times\frac{8}{17}+\frac{4}{9}\times\frac{8}{17}\)

\(=\left(\frac{5}{9}+\frac{4}{9}\right)\times\frac{8}{17}\)

\(=1\times\frac{8}{17}\)

\(=\frac{8}{17}\)

      \(\frac{5}{9}x\frac{8}{17}+\frac{4}{9}x\frac{8}{17}\)

\(=\frac{8}{17}x\left(\frac{5}{9}+\frac{4}{9}\right)\)

\(=\frac{8}{17}x\frac{9}{9}\)

\(=\frac{8}{17}x1\)

\(=\frac{8}{17}\)

5/9 x 8/17 + 4/9 x 8/17 

= ( 5/9 + 4/9 ) x 8/17 

= 1 x 8/17 

= 8/17 

\(\frac{1}{3}x\)\(\frac{1}{2}-\frac{1}{5}x\)\(\frac{1}{2}\)

=(\(\frac{1}{3}-\frac{1}{5}\)) x \(\frac{1}{2}\)

=\(\frac{2}{15}x\)\(\frac{1}{2}\)

=\(\frac{1}{15}\)

1/3 * 1/2 - 1/5 * 1/2

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

=8/15*1/2

=4/15

1\3x1\2-1\5x1\2=1\3 x1\2-1\5x1\2=1\7-1\6=1\1=1

12/15 + 37/7 + 16/5 + 5/7 = 10

12/15 + 37/7 + 16/5 + 5/7

= 4/5 + 37/7 + 16/5 + 5/7

= (4/5 + 16/5) + (37/7 + 5/7)

= 4 + 6

= 10

Chúc bạn học tốt.

😁😁😁

12/15 + 37/7 + 16/5 + 5/7

= ( 37/7 + 5/7 ) + ( 12/15 + 16/5 )

= 6 + ( 12/15 + 48/15 )

= 6 + 4 

= 10

Bổ ích thì k cho c em nha!

(3/5+5/8)+(3/4+1/2)=49/40+5/4=99/40

39/17

39/17

  12/17 + 19/17 + 8/17

=         31/17 + 8/17

=            39/17

Vậy.... [kết luận]