2. 4* (2,2а - 20в) + 6а *0,2 = 8,8а - 80в + 1,2а = 10а - 80в = 10*40 - 80*0,4 = 400- 16 = 384
3.а) 5,38х - 8,54 + 2,92х = 9,72
8,3х = 9,72 + 8,54
8,3х = 18,26
х = 18,26/8,3
х = 2,2
б) 15 16/33 + х + 4 21/33 = 27 2/33
х = 27 2/33 - 4 21/33 - 15 16/33
х = (27 - 4 - 15) + (2/33 - 21/33 - 16/33) = 8 + (- 35/33) = 6 31/33