Ответ:\(0.2x+1.1x=14.1-2.7\); \(1.3x=11.4\); \(x=114/13\).\(3.9+2x=7x-16.1\); \(20=5x\); \(x=4\).\(9-7x-21=5-3x\); \(-12-7x=5-3x\); \(-4x=17\); \(x=-17/4\).\(-2x+10+3x-12=6x+11\); \(x-2=6x+11\); \(-5x=13\); \(x=-13/5\).