1) -3(0,2x+0,4y)+(1,6x+2,8y)= -0,6x-1,2y+1,6x+2,8y=x+1,6y
2) 2/7*(4.2/3 m-1,4)-2/9(6m+2,7)=2/7(14/3 m-7/5)-2/9(6m+27/10)=
=4/3 m- 2/5 -4/3m - 3/5 = -5/5=-1
3) 8m +14n -9m-15n +7n =-m +6n
4) -0,4y * (-0,8) = -0,96; 0,32y = -0,96; y=-0,96/0,32; y=-3
5) 8/9 *3.3/5*(-2,1x)=20,16; 8/9 *18/5*(-21/10x)=20,16;
-168/25 x=20,16; -6,72x=20,16; x=-20,16/6,72; x=-3