)1,2(5\6R+0.4n))-1.8(5\6R-0.3n)=
12/10*5/6R+12/10*4/10n-18/10*5/6R+18/10*3/10=
R+12/25n-3/2R+27/50=
-1/2R+1 1/50;//////
6)(1\6a+6.5)-(2 7\9a+3 1\3)=
1/6а+6,5-2 7/9а-3 1/3=
3/18а-2 14/18а+13/5-10/3=
-2 11/18а+39/15-50/15=
-2 11/18а-11/15;///
7)3\7(0.56x-4.9y)-6\13(0.52x-3.9y)=
3/7*14/25х-3/7*49/10у-6/13*13/25х+6/13*39/10у=
6/25х-21/10у-6/25х+9/5у=
-21/10у+18/10у=-3/10у;////.
8)6(1\4R-5\6)-15(0.6-2 1\3R)=
6/1*1/4R-6/1*5/6-15/1*6/10+15/1*7/3R=
3/2R-5-9+35R=36 1/2R-14