очень
5x−0,4y=32
0,4x+1,4y=1

5х-0,4+0.4+1.4у=32+1

5х+1.4у=33

5х=33-1.4у

х=33-1.4у/5

х=6.6-0.28у

5(6.6-0.28у)+1.4у=33

5×6.6-5×(-0.28)+1.4у=33

33-(-1.4)+1.4у=33

33+1.4+1.4у=33

1.4у=33-33-1.4

1.4у=-1.4

у=-1

х=6.6-0.28×(-1)

х=6.6+0.28

х=6.88