1
设飞机平局速度x,风速度Y
2.5*(x+y)=1200
(10/3)*(x-y)=1200
2
x张制盒身,y张盒底
x*25=80y
x+y=36
3
设上坡x,平坡y,
x/3+y/4=54/60
x/5+y/4=42/60