Question

若X/3=Y/4=Z/5,求（X+Y)/(X-2Y+3Z)的值

Answer 1

x/3=y/4=z/5=k
x=3k y=4k z=5k
原式=7k/3k-8k+15k=7/10

Answer 2

令X/3=Y/4=Z/5=k,所以（X+Y)/(X-2Y+3Z)=（3K+4k)/(3k-8K+15k)=7/10

Answer 3

用x=3，y=4，z=5直接往里带就行了。