$#Shả$

`A)=5/17xx(15/34+19/34)`

`=5/17xx1=5/17`

`B)=(13/12+7/12)+1/3`

`=5/3+1/3=2`

12/17+8/17=20/17+19/17=39/17

39/17

39/17

  12/17 + 19/17 + 8/17

=         31/17 + 8/17

=            39/17

Vậy.... [kết luận]

(13/17-5/17):8/3

=8/17:8/3

=3/17

=\(\dfrac{13}{17}:\dfrac{8}{3}-\dfrac{5}{17}:\dfrac{8}{3}\)

=\(\left(\dfrac{13}{17}-\dfrac{5}{17}\right):\dfrac{8}{3}\)

=\(\dfrac{8}{17}:\dfrac{8}{3}\)

\(=\dfrac{3}{17}\)

\(\dfrac{13}{17}:\dfrac{8}{3}-\dfrac{5}{17}:\dfrac{8}{3}=\dfrac{13}{17}.\dfrac{3}{8}-\dfrac{5}{17}.\dfrac{3}{8}=\dfrac{3}{8}\left(\dfrac{13}{17}-\dfrac{5}{17}\right)=\dfrac{3}{8}.\dfrac{8}{17}=\dfrac{3}{17}\)

\(\frac{15}{34}-\frac{5}{17}+\frac{19}{34}-\frac{12}{17}\)

\(=\left(\frac{15}{34}+\frac{19}{34}\right)-\left(\frac{5}{17}+\frac{12}{17}\right)\)

\(=1-1=0\)

\(\frac{15}{34}-\frac{5}{17}+\frac{19}{34}-\frac{12}{17}\)

\(=\left(\frac{15}{34}+\frac{19}{34}\right)-\left(\frac{5}{17}+\frac{12}{17}\right)\)

\(=\frac{34}{34}-\frac{17}{17}\)

\(=1-1\)

\(=0\)

\(\frac{15}{34}-\frac{5}{17}+\frac{19}{34}-\frac{12}{17}\)

=\(\frac{15}{34}+\frac{19}{34}-\frac{5}{17}-\frac{12}{17}\)

=\(1-\frac{5}{17}-\frac{12}{17}\)

=\(1-\left(\frac{5}{17}+\frac{12}{17}\right)\)

=\(1-1\)

=\(0\)

1a) \(\frac{12}{17}+\frac{19}{17}+\frac{8}{17}\)

\(=\left(\frac{12}{17}+\frac{8}{17}\right)+\frac{19}{17}\)

\(=\frac{20}{17}+\frac{19}{17}\)

\(=\frac{39}{17}\)

b) \(\frac{2}{5}+\frac{7}{12}+\frac{13}{12}\)

\(=\frac{2}{5}+\frac{5}{3}\)

\(=\frac{31}{15}\)

2) \(\frac{25}{3}-x=\frac{5}{6}\)

                \(x=\frac{25}{3}-\frac{5}{6}\)

                \(x=\frac{45}{6}\)

ủng hộ tớ nha

dấu ''/'' là chia à bạn?

ai giúp mình với

b) 13/17 : 8/3 - 5/17 : 8/3

= ( 13/17 -  5/17 ) : 8/3

= 7/17  *  3/8

=21/136

c) 1/6 + 1/12 + 1/20 + 1/20

= (1/6 + 1/12) + (1/20 + 1/20)

= (2/12 + 1/12) + (1/20 + 1/20)

=  3/12  +  2/20

=  1/4 +2/20

= 5/20 + 2/20

=  7/20

\(b)\frac{13}{17}\div\frac{8}{3}-\frac{5}{17}\div\frac{8}{3}\)

\(=\left(\frac{13}{17}-\frac{5}{17}\right)\div\frac{8}{3}\)

\(=\frac{8}{17}\div\frac{8}{3}\)

\(=\frac{3}{17}\)

\(c)\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{20}\)

\(=\left(\frac{2}{12}+\frac{1}{12}\right)+\left(\frac{1}{20}+\frac{1}{20}\right)\)

\(=\frac{1}{4}+\frac{2}{20}\)

\(=\frac{5}{20}+\frac{2}{20}=\frac{7}{20}\)

(13/17 - 5/17) : 8/3 = 8/17 : 8/3 = 3/17

1/6+1/12+1/20 nhân 1=(1/6+1/12)+1/20=1/4 +1/20=6/20=3/10

đây nha em.

\(=\left(3,72+6,28\right)+\left(2,05+7,95\right)=10+10=20\)