1) а) 3х – 4х = 55 – 11; –х = 44; х = –44; б) –4х + 8х = 45 + 15; 4х = 60; х = 15; в) –8х – 3х = –105 + 17; –11х = –88; х = 8. 2) а) 2у + 6 = 21 – 3у; 2у – 3у = 21 – 6; –у = 15; у = –15; б) 2 – с + 3с – 9 = –13; 2с = –13 + 9 – 2; 2с = –6; с = –3; в) –3 + 9b – 12 = 12; 9b = 12 + 12 + 3; 9b = 27; b = 3.