Ж) 2/9(1,8m-5,4)-3/7(2,1m-4,2) = 2/9(18/10m-54/10) - 3/7 (21/10m- 42/10) = 2/5m - 6/5 - 9/10m+9/5 = 2/5m -9/10m -6/5+9/5= 4-9 /10m - 6+9/ 5= -1/2m - 3
з) 1/3(0,3y-0,6)-1/4(0,4y-0,8) = 1/3 (3/10y - 6/10) - 1/4 (4/10y-8/10) = 1/10y - 1/5 - 1/10y + 1/5= 0