Ответ:\(9x-7=21-5x\); \(14x=28\); \(x=2\).\(4x-20=x+4\); \(3x=24\); \(x=8\).\(8-40-15x=13\); \(-15x=45\); \(x=-3\).\(-5x=11-8x+4\); \(3x=15\); \(x=5\).