{X+2Y/2+3X-Y/3=5{0.2(X+2Y)+0.8(3X-Y)=4

令a=x+2y
b=3x-y
a/2+b/3=5 (1)
0.2a+0.8b=4 (2)
所以a=20-4b
代入(1)
10-2b+b/3=5
5b/3=5
b=3
a=20-4b=8
所以x+2y=8 (3)
3x-y=3 (4)
(4)×2+(3)
7x=14
x=2
y=3x-3=3