`a: =(7/3-4/3)+11/5=16/5`

`b: =(18/13-5/13)+55/46=1+55/46=101/46`

`c: =27/25-4/9-2/25+5/9=(27/25-2/25)+(5/9-4/9)=1+1/9=10/9`

\(a,\frac{12}{25}+\frac{3}{5}+\frac{13}{25}\)

\(=\left(\frac{12}{25}+\frac{13}{25}\right)+\frac{3}{5}\)

\(=\frac{25}{25}+\frac{3}{5}\)

\(=1+\frac{3}{5}\)

\(=\frac{8}{5}\)

\(b,\frac{3}{2}+\frac{2}{3}+\frac{4}{3}\)

\(=\frac{3}{2}+\left(\frac{2}{3}+\frac{4}{3}\right)\)

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

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

\(c,\frac{3}{5}+\frac{7}{5}+\frac{3}{4}\)

\(=\left(\frac{3}{5}+\frac{7}{5}\right)+\frac{3}{4}\)

\(=2+\frac{3}{4}\)

\(=\frac{11}{4}\)

\(1,\dfrac{12}{25}+\dfrac{3}{5}+\dfrac{13}{25}=\left(\dfrac{12}{25}+\dfrac{13}{25}\right)+\dfrac{3}{5}=1+\dfrac{3}{5}=\dfrac{8}{5}\\ 2,\dfrac{3}{2}+\dfrac{2}{3}+\dfrac{4}{3}=\dfrac{3}{2}+\left(\dfrac{2}{3}+\dfrac{4}{3}\right)=\dfrac{3}{2}+2=\dfrac{7}{2}\\ 3,\dfrac{3}{2}+\dfrac{7}{5}+\dfrac{3}{4}=\left(\dfrac{3}{2}+\dfrac{3}{4}\right)+\dfrac{7}{5}=\left(\dfrac{6}{4}+\dfrac{3}{4}\right)+\dfrac{7}{5}=\dfrac{9}{4}+\dfrac{7}{5}=\dfrac{45}{20}+\dfrac{28}{20}=\dfrac{73}{20}\)

Quy đồng 3/5 cho cùng mẫu chung là 25 có

12/25+15/25+13/25=40/25=8/5

Mẫu chung là 6 có

9/6+4/6+8/6=21/6=7/2

Quy đồng mẫu chung là 20 có

30/20+28/30+15/20=73/20

Chúc em học tốt

     12/25 + 3/5 + 13/25 = (12/25 +13/25) + 3/5 = 1 + 3/5 = 8/5

   3/2 + 2/3 + 4/3 =3/2  + ( 2/3+4/3 ) = 7/2

    3/2 + 7/5 + 3/4 = ( 3/2+3/4) + 7/5 = 12/5

a. 12/25 + 3 / 5+ 13/25 = ( 12/25+13/25)+3/5 = 1 + 3/5= 8/5

b. 3/2 + 2/3 + 4/3 = 3/2+( 2/3+4/3)= 3/2 + 2=7/2

c.3/5+7/5+3/4= (3/5+7/5)+3/4 = 2+ 3/4=11/4 

chúc bn hc tốt 

a. 12/25+3/5+13/25

=1+3/5

=8/5

b.3/2+2/3+4/3

=3/2+2

=7/2

c.3/5+7/5+3/4

=2+3/4

=11/4

812 x 5 + 812 x 7 - 7 - 812 x 2 ???

 toàn câu hỏi sai

=1500