\(26\times\dfrac{13}{42}:13\\ =26\times\dfrac{13}{42}\times\dfrac{1}{13}\\ =26\times\dfrac{1}{42}=13\times\dfrac{1}{21}=\dfrac{13}{21}\)

=11/7x(7/13+17/13)

=11/7x24/13

=264/91

264/91

=(1/13+12/13)+(2/13+11/13)+(3/13+10/13)+......(6/13+7/13)

=1+1+1+1+1+1

=6

\(=\frac{1+2+3+...+12}{13}\)

\(=\frac{\left(12+1\right)+\left(11+2\right)+..+\left(5+7\right)+6}{13}\)

\(=\frac{12+12+12+12+12+6}{13}\)

\(=\frac{12.5+6}{13}\)

\(=\frac{66}{13}\)

Cảm ơn bạn nhiều nhé!!!

( − 4 ) .13. ( − 250 ) = ( − 4 ) . ( − 250 ) .13 = 1000.13 = 13000

\(\dfrac{4}{13}:\dfrac{1}{15}\times\dfrac{1}{15}:\dfrac{4}{13}\\ =\left(\dfrac{4}{13}:\dfrac{4}{13}\right)\times\left(\dfrac{1}{15}:\dfrac{1}{15}\right)\\ =1\times1\\ =1.\)

=\(\dfrac{13}{22}\cdot4+\dfrac{4}{22}\cdot4=\dfrac{4}{22}\left(13+4\right)=\dfrac{4}{22}\cdot17=\dfrac{2}{11}\cdot17=\dfrac{34}{11}\)

mình đag cần gấp 

(5/6-13/19) - (17/30-13/19)

=(13/19-13/19)-(5/6-17/30)

=0-4/15

=4/15

\(\left(\frac{5}{6}-\frac{13}{19}\right)-\left(\frac{17}{30}-\frac{13}{19}\right)\)

\(=\frac{5}{6}-\frac{13}{19}-\frac{17}{30}+\frac{13}{19}\)

\(=\left(\frac{5}{6}-\frac{17}{30}\right)+\left(\frac{-13}{19}+\frac{13}{19}\right)\)

\(=\frac{4}{15}+0\)

\(=\frac{4}{15}\)

\(\dfrac{7}{5}+\dfrac{8}{5}+\dfrac{7}{2}+\dfrac{1}{2}+\dfrac{12}{13}+\dfrac{27}{13}=\dfrac{15}{5}+\dfrac{8}{2}+\dfrac{39}{13}=3+4+3=10\)

a) \(\dfrac{7}{5}+\dfrac{7}{2}+\dfrac{8}{5}+\dfrac{12}{13}+\dfrac{1}{2}+\dfrac{27}{13}=\left(\dfrac{7}{5}+\dfrac{8}{5}\right)+\left(\dfrac{7}{2}+\dfrac{1}{2}\right)+\left(\dfrac{12}{13}+\dfrac{27}{13}\right)\)\(=3+4+3=10\)

= ( 7/5+ 8/5) + ( 7/2+ 1/2) + ( 12/13+ 27/13)

= 3 + 4+ 3

= 10