9/5:17/15+8/5:17/15

=27/17    +   24/17

=51/17=3

C1: \(\frac{9}{5}\div\frac{17}{15}+\frac{8}{5}\div\frac{17}{15}\)

 \(=\frac{27}{17}+\frac{24}{17}\)

\(=3\)

C2: \(\frac{9}{5}\div\frac{17}{15}+\frac{8}{5}\div\frac{17}{15}\)

\(=\left(\frac{9}{5}+\frac{8}{5}\right)\div\frac{17}{15}\)

\(=\frac{17}{5}\div\frac{17}{15}\)

\(=3\)

C1: 9/5:17/15+8/5:17/15

= 27/17 + 24/17

=3

C2: 9/5:17/15+8/5:17/15

= (9/5+8/5):17/15

=17/1:17/15

=3

C1:(9/5+8/5):17/15=17/5:17/15=3(nhớ bình chọn nha)

C2;27/17+24/17=3(nhớ bình chọn nha)

cách 1: \(\frac{9}{5}:\frac{17}{15}+\frac{8}{5}:\frac{17}{15}=\frac{9}{5}.\frac{15}{17}+\frac{8}{5}.\frac{15}{17}=\frac{15}{17}.\left(\frac{9}{5}+\frac{8}{5}\right)=\frac{15}{17}.\frac{17}{5}=3\)

cách 2: \(\frac{9}{5}:\frac{17}{15}+\frac{8}{5}:\frac{17}{15}=\frac{9}{5}.\frac{15}{17}+\frac{8}{5}.\frac{15}{17}=3.\frac{3}{17}+8.\frac{3}{17}=\frac{27}{17}+\frac{24}{17}=\frac{51}{17}=3\)

a)

C1: 9/5 : 17/15 + 8/5 : 17/15

= 27/17 + 14/17

= 3

C2: 9/5 : 17/15 + 8/5 : 17/15

= ( 9/5 + 8/5 ) : 17/15

= 17/5 : 17/15

= 3

b)

C1: 0,9 : 0,25 + 1.05 : 0,25

= 3,6 + 4,2

= 7,8

C2: 0,9 : 0,25 + 1,05 : 0,25

= ( 0,9 + 1,05) : 0,25

= 1,95 : 0,25

= 7,8

 A) cách 1\(\frac{9}{5}:\frac{17}{15}+\frac{8}{5}:\frac{17}{15}\)

\(=\frac{9}{5}\cdot\frac{15}{17}+\frac{8}{5}\cdot\frac{15}{17}\)

\(=\frac{135}{85}+\frac{120}{85}\)

\(=\frac{255}{85}\)

\(=3\)

Cách 2\(\frac{9}{5}:\frac{17}{15}+\frac{8}{5}:\frac{17}{15}\)

\(=\frac{9}{5}\cdot\frac{15}{17}+\frac{8}{5}\cdot\frac{15}{17}\)

\(=\frac{15}{17}\cdot\left(\frac{9}{5}+\frac{8}{5}\right)\)

=\(\frac{15}{17}\cdot\frac{17}{5}\)

\(=\frac{15\cdot17}{17\cdot5}\)

\(=\frac{5\cdot3\cdot17}{17\cdot5}\)

\(=3\)

B) Cách 1 :

0,9 : 0,25 + 1,05 : 0,25

= 3,6 + 4,2

=7,8

Cách  2:

0,9 : 0,25 + 1,05 : 0,25

\(=0,9:\frac{1}{4}+1,05:\frac{1}{4}\)

\(=0,9\cdot4+1,05\cdot4\)

\(=4\cdot\left(0,9+1,05\right)\)

\(=4\cdot1,95\)

=\(7,8\)