=6(0.84+0.16)=6×1=6
=0.77(23+77)=0.77×100=77
=3/7(4/17-4/17)=0
=16/72(-25/72-11/72)=16/72×(-36/72)=-1/9
=19/20(2/19-3/7+3/7)=19/20×2/19=1/10
2 1/12, 2 2/7, 1 10/7, 2 3/5, 3 11/20, 4 11/45,
4 11/13, 4 143/165,
<span>0,25/х+0,2=-3/20
</span><span>0,25/х=-3/20-0,2
</span><span>0,25/х=-3/20-4/20
</span><span>0,25/х=-7/20
х=25/100:(-7/20)
х=1/4*(-20/7)
х=(-5/7)</span>
Х-80=640*40. Х-80=25600. Х=25600+80. Х=25680.
Это очень легко. за 6 часов .