已知x:y:z=3:4:5,3x+2y-4z=18.求:x+y+z.

问题描述:

已知x:y:z=3:4:5,3x+2y-4z=18.求:x+y+z.
如题.

X=3K,Y=4K,Z=5K
3X+2Y-4Z=18
9K+8K-20K=18
K=-6
X=-18,Y=-24,Z=-30
X+Y+Z=-72