设宽度为d;
1) (2d+8)*(2d+6)=80
d=1dm;
2) 6/8=(6+2x)/(8+2y)
y=4x/3;
3) s=(6+2x)(8+2y)=(6+2x)(8+2*4x/3)=108
x=1.5dm
y=2dm;