(4х + 3у) / (4х - 3у) =

= (-3 - 1/2) / (-3 + 1/2) =

= -3 1/2 : (-2 1/2) =

= 7/2 : 5/2 =

= 7/2 * 2/5 = 7/5 = 1 2/5,

-4в+6+12в-8 = 8в - 2,

15а-а-3+2а-1 = 16а - 4,

5а-6а+7а-8а+9 = 9 - 2а