0,4=4/10, 1 целая3/7=10/7, 0,9=9/100,4*(0,9-5/7х)-0,9*(0,4*1 целую 3/7х)= (0,36-2/7х)-0,9*(4/10* 10/7)=(0,36-2/7х)-0,9* 4/7=0,36-2/7х-18/35х=0,36-10/35х-18/35х=0,36-28/35х= 0,36-4/5х=0,36-0,8х=0,4*(0,9-0,2х)
3*(5m-4n)-4*(3m-2n)=15m-12n-12m+8n=3m-4n=3*(-0.2)-4*0.7=-0.6-2.8=-3.4