若x/3=y/4=z/5，则-x+y/x+2y+3z=_．
问题描述：
若
=x 3
=y 4
，则z 5
=______． -x+y x+2y+3z
答
设
=x 3
=y 4
=k，z 5
则x=3k，y=4k，z=5k，
所以
=-x+y x+2y+3z
=-3k+4k 3k+2×4k+3×5k
．1 26
故答案为：
．1 26