a)1/5.(4/7+3/7+1/5)

=1/5.(1+1/5)

=1/5.4/5

=4/25

b)-1/9.(-3/5)+5/-6.(-3/5)-7/2.3/5

=1/9.3/5+5/6.3/5-7/2.3/5

=3/5.(1/9+5/6-7/2)

=3/5.(2/18+15/18-63/18)

=3/5.(-46/18)

=3/5.(-23/9)

=-69/45

=-23/15

c)5/13​+(−5/7​)+(−20​/41)+8/13+(−21/41​)

=(5/13+8/13)+(−20/41+−21/41)+(−5/7)

=1+(−1)+(−5/7)

=0+(−5/7)=−5/7

​d)d)6/7.8/13+6/7.9/13-3/13.6/7

=6/7.(8/13+9/13-3/13)

=6/7.14/13

=84/91

=12/13

e)-3/7.15/13-3/7.11/13-3/7

=-3/7.(15/13-11/13-3/7)

=-3/7.-11/91

=33/637

f)-5/9 + 8/15 + -2/11 + 4/-9 + 7/15
=(-5/9-4/9)+(8/15+7/15)-2/11
=-9/9+15/15-2/11
=-1+1-2/11

=0-2/11=-2/11