设x/2=y/3=z/5=k则x=2k，y=3k，z=5kx+y+z=2k+3k+5k=10k=15k=15/10=3/2x=3，y=9/2，z=15/2
设x/2=y/3=z/5＝k(这是解这类题的关键）所以x=2k,y=3k,z=5k代入x+y+z=15得k=1.5所以：x=3,y=4.5,z=7.5
