c1                           {3/4+1/2}*5/7

                               =5/4*5/7

                               =25/28 

c2                          {3/4+1/2}*5/7

                               = 3/4*5/7+1/2*5/7

                               =15/28+5/14

                               =25/28

a)1 /3 +1/4+2/3+3/4=\(\frac{1}{3}\)+\(\frac{2}{3}\)+\(\frac{1}{4}\)+\(\frac{3}{4}\)=1+1=2

b)1/2 +/3 -/5 +1/6=4/5

a,1/3+1/4+2/3+3/4   

=(1/3+2/3)+(1/4+3/4)

=      1      +      1

=              2

nha, còn phàn b mình chưa biết

a)\(\frac{1}{3}\)+\(\frac{1}{4}\)+\(\frac{2}{3}\)+\(\frac{3}{4}\)

=(\(\frac{1}{3}\)+\(\frac{2}{3}\))+(\(\frac{1}{4}\)+\(\frac{3}{4}\))

=1+1

=2

\((\frac{3}{5}+\frac{2}{5})+(\frac{4}{7}+\frac{1}{7}+\frac{2}{7})\) ) =1+1=2

a) 2 x 3/4 + 2 x 1/4 = 2 x (3/4 + 1/4)

                             = 2 x 1

                             = 2

b) 3 x 2/3 - 3 x 1/3  = 3 x (2/3 - 1/3)

                             = 3 x 1/3

                             = 1

A : 2 . 3/4 + 2 . 1/4

=3/2 + 1/2

= 2

B : 3.2/3-3.1/3

=2-1

=1

a: \(1\dfrac{1}{2}\cdot1\dfrac{1}{3}\cdot1\dfrac{1}{4}\)
\(=\dfrac{3}{2}\cdot\dfrac{4}{3}\cdot\dfrac{5}{4}\)

\(=\dfrac{5}{2}\)

b: \(1\dfrac{1}{2}:1\dfrac{1}{3}:1\dfrac{1}{4}\)

\(=\dfrac{3}{2}:\dfrac{4}{3}:\dfrac{5}{4}\)

\(=\dfrac{3}{2}\cdot\dfrac{3}{4}\cdot\dfrac{4}{5}=\dfrac{9}{10}\)