Question

已知x:y=3:5,y:z=2:3,求（x+y+z）/(2x-y+z)的值.

Answer 1

x:y=3:5=6:10 y:z=2:3=10:15

所以x:y:z=6:10:15 所以 x/6=y/10=/z/15=t

x=6t y=10t z=15t

（x+y+z）/(2x-y+z) =(6t+10t+15t)/(12t-10t+15t)= 31/17