已知x:y:z=4:5:7,求3x-2y+z/2x+3y+z的值
问题描述：
已知x:y:z=4:5:7,求3x-2y+z/2x+3y+z的值
答
3/10
答
x:y:z=4:5:7
设x=4t y=5t z=7t
3x-2y+z/2x+3y+z
=12t-10t+7t/8t+15t+7t
=9t/30t
=3/10