a/\(\dfrac{1}{2}\).\(\dfrac{4}{3}\)-\(\dfrac{20}{3}\).\(\dfrac{4}{5}\)

=\(\dfrac{2}{3}\)-\(\dfrac{16}{3}\)

=\(\dfrac{-14}{3}\)

b/\(\dfrac{3}{7}\)+\(\dfrac{-6}{19}\)+\(\dfrac{4}{7}\)+\(\dfrac{-13}{19}\)

=(\(\dfrac{3}{7}\)+\(\dfrac{4}{7}\))+(\(\dfrac{-6}{19}\)+\(\dfrac{-13}{19}\))

=1+(-1)

=0

c/\(\dfrac{3}{5}\).\(\dfrac{8}{9}\)-\(\dfrac{7}{9}\).\(\dfrac{3}{5}\)+\(\dfrac{3}{5}\).\(\dfrac{26}{9}\)

=\(\dfrac{3}{5}\).(\(\dfrac{8}{9}\)-\(\dfrac{7}{9}\)+\(\dfrac{26}{9}\))

=\(\dfrac{3}{5}\).\(\dfrac{27}{9}\)

=\(\dfrac{81}{45}\)

=\(\dfrac{9}{5}\)

a)\(\dfrac{-5}{9}\)+\(\dfrac{8}{15}\)+\(\dfrac{-2}{11}\)+\(\dfrac{4}{-9}\)+\(\dfrac{7}{15}\)

=\(\dfrac{-9}{9}\)+\(\dfrac{15}{15}\)+\(\dfrac{-2}{11}\)

=-1+1+\(\dfrac{-2}{11}\)

=0+\(\dfrac{-2}{11}\)

=\(\dfrac{-2}{11}\)

b)(\(\dfrac{7}{2}\).\(\dfrac{5}{6}\))+(\(\dfrac{7}{6}\):\(\dfrac{2}{7}\))

=\(\dfrac{7}{2}\).(\(\dfrac{5}{6}\)+\(\dfrac{7}{6}\))

=\(\dfrac{7}{2}\).\(2\)

=7

a/Có -3/8=-9/24;5/-12=-10/12

Vì -9/24>-10/24 nên -3/8>5/-12

b/Có 3131/5252=31/53

Vậy 3131/5252=31/52