1)=4/3-1/3log(2)15+1/3log(2)20=4/3-1/3*log(2)15+1/3log(2)20=
1/3*(4-log(2)5-log(2)3+log(2)4+log(2)5))=
=1/3*(6-log(2)3)=2-(log(2)3)/3
2)=log(8)(16/15 *20)=
log(8)(16*4/3)=
log(8)(64*3)=log(8)64-
log(8)3=2-1/3*log(2)3
3) =log(8)(12/15*20)=
log(8)(12*4/3)=
log(8)(48/3)=log(8)48-
log(8)3=1+log(8)6-
log(8)3=1+log(8)2=
1+1/3=4/3