1) 3(х+5)=7-5х ; 3х+15=7-5х; 3х+5х=7-15;
8х=-8; х=-8:8; х=-1; /////
2) 19(у-9)=3(у+7); 19у-171=3у+21; 19у-3у=21+171; 16у=192; у=192:16; у=12; // //
3) (х-9) =3(х-8) ; х-9=3х-24; х-3х=-24+9; -2х=-15; х=15:2; х=7,5 //////
4) 3(2х-9)=15(1-х); 6х-27=15-15х;
6х+15х=15+27; 21х=42; х=42:21; х=2; ////
5) 7(3-2х)=15(1-х) ;,21-14х=15-15х;
-14х+15х=15-21; х=-6;