`a) 5 / 13 xx 4 / 15 xx 13 = [ 5 xx 4 xx 13 ] / [ 13 xx 5 xx 3 ] = 4 / 3`

`b) ( 3 / 7 + 5 / 2 ) xx 7 / 5 = 3 / 7 xx 7 / 5 + 5 / 2 xx 7 / 5 = 3 / 5 + 7 / 2 = 6 / 10 + 35 / 10 = 41 / 10`

`c) 1 / 5 xx 11 / 18 + 11 / 18 xx 3 / 5 = 11 / 18 xx ( 1 / 5 + 3 / 5 ) = 11 / 18 xx 4 / 5 = [ 11 xx 2 xx 2 ] / [ 2 xx 9 xx 5 ] = 22 / 45`

\(a,\dfrac{5}{13}\times\dfrac{4}{15}\times13=\dfrac{4}{3}\)

\(b,\left(\dfrac{3}{7}+\dfrac{5}{2}\right)\times\dfrac{7}{5}=\left(\dfrac{6}{14}+\dfrac{35}{14}\right)\times\dfrac{7}{5}=\dfrac{41}{14}\times\dfrac{7}{15}=\dfrac{41}{30}\)

\(c,\dfrac{1}{5}\times\dfrac{11}{18}+\dfrac{11}{18}\times\dfrac{3}{5}=\dfrac{11}{18}\times\left(\dfrac{1}{5}+\dfrac{3}{5}\right)=\dfrac{11}{18}\times\dfrac{4}{5}=\dfrac{22}{45}\)

\(a,\dfrac{5}{13}\times\dfrac{4}{15}\times13=\dfrac{5\times4\times13}{13\times5\times3}=\dfrac{4}{3}\\ b,\left(\dfrac{3}{7}+\dfrac{5}{2}\right)\times\dfrac{7}{5}=\dfrac{3}{7}\times\dfrac{7}{5}+\dfrac{5}{2}\times\dfrac{7}{5}=\dfrac{3}{5}+\dfrac{7}{2}=\dfrac{6}{10}+\dfrac{35}{10}=\dfrac{41}{10}\\ c,\dfrac{1}{5}\times\dfrac{11}{18}+\dfrac{11}{18}\times\dfrac{3}{5}=\dfrac{11}{18}\times\left(\dfrac{1}{5}+\dfrac{3}{5}\right)=\dfrac{11}{18}\times\dfrac{4}{5}=\dfrac{22}{45}\)

a, 4/3  b, 41/10   c,22/45

 36-4x9 = 36 - 36 = 0 Vì số nào nhân với 0 thì cũng bằng 0 nên phép tính đó bằng 0

a,18/15+7/15+12/15=18+7+12/15

                             =37/15

b,9/7+8/7+11/7=9+8+11/7

                      =28/7=1/4

+8/15 + 7/15 +12/15 = (18+7+12)/7 = [(18+12)+7]/15= (30+7)/15=37/15=7/3

9/7 + 8/7 + 11/7 = (9+8+11)/7= [(9+11)+8]/7=(20+8)/7= 28/7 =4

a) \(\frac{18}{15}+\frac{7}{15}+\frac{12}{15}\)

= \(\frac{18+7+12}{15}\)

= \(\frac{37}{15}\)

b) \(\frac{9}{7}+\frac{8}{7}+\frac{11}{7}\)

= \(\frac{9+8+11}{7}\)

= \(\frac{28}{7}\)

a) 18/15 + 7/15 + 12/15

= (18/15 + 12/15) + 7/15

= 30/15 + 7/15

= 37/15

b) 9/7 + 8/7 + 11/7

= (9/7 + 11/7) + 8/7

= 20/7 + 8/7

= 28/7

chuc ban hok tot

a)18/15+7/15+12/15=(18/15+12/15)+7/15=30/15+7/15=37/15

b)9/7+8/7+11/7=(9/7+11/7)+8/7=20/7+8/7=28/7=4

đúng thì k cho mik nha

a ) \(\frac{1}{15}+\frac{4}{15}+\frac{5}{18}+\frac{7}{18}\)

\(=\left(\frac{1}{15}+\frac{4}{15}\right)+\left(\frac{5}{18}+\frac{7}{18}\right)\)

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

\(=1\)

b ) \(\frac{1}{8}+\frac{1}{12}+\frac{3}{8}+\frac{5}{12}\)

\(=\left(\frac{1}{8}+\frac{3}{8}\right)+\left(\frac{1}{12}+\frac{5}{12}\right)\)

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

\(=1\)

a, \(\frac{1}{15}\)+    \(\frac{4}{15}\)+    \(\frac{5}{18}\)+    \(\frac{7}{18}\)=    ( \(\frac{1}{15}\)+    \(\frac{4}{15}\)) + ( \(\frac{5}{18}\)+    \(\frac{7}{18}\))

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

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

b,\(\frac{1}{8}\)+    \(\frac{1}{12}\)+ \(\frac{3}{8}\)+    \(\frac{5}{12}\)=    ( \(\frac{1}{8}\)+    \(\frac{3}{8}\)) + ( \(\frac{1}{12}\)+    \(\frac{5}{12}\))

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

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

1)     \(\frac{1}{12}+\frac{1}{16}+\frac{3}{4}\)

\(=\frac{4}{48}+\frac{3}{48}+\frac{36}{48}\)

\(=\frac{4+3+36}{48}\)

\(=\frac{43}{48}\)

2)   a)    \(\frac{1}{15}+\frac{4}{15}+\frac{5}{18}+\frac{7}{18}\)

\(=\left(\frac{1}{15}+\frac{4}{15}\right)+\left(\frac{5}{18}+\frac{7}{18}\right)\)

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

b)    \(\frac{1}{8}+\frac{1}{12}+\frac{3}{8}+\frac{5}{12}\)

\(=\left(\frac{1}{8}+\frac{3}{8}\right)+\left(\frac{1}{12}+\frac{5}{12}\right)\)

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

a) 18/15 + 7/15 + 12/15 =18/15 + 12/15 + 7/15        

                                    = 30/15 + 7/15

                                     =       37/15

b) 9/7 + 8/7 +11/7 = 9/7 + 11/7 + 8/7 

                         =  20/7  + 8/7 =  28/7 nha . tk mk nhé b

a, 18/15+7/15+12/15= 37/15

b, 9/7+8/7+11/7=28/7=4

a ) \(\frac{18}{15}\)+ \(\frac{7}{15}\)+ \(\frac{12}{15}\)= \(\frac{37}{15}\)

b )\(\frac{9}{7}\)+ \(\frac{8}{7}\)+ \(\frac{11}{7}\)= 4