19х:2-91y:2 = 1991 (19x - 91y): 2 = 1991 19х:2 = 199191у:2) 1991 : (-91у) : 2-91 = 1991 91у : 2 =1991-1991+91 91y : 2 = 91 40,5у = 91 у= 91:40,5 у= 2