已知3x+y+2z=28,5x-3y+z=7,求x+y+z的值

问题描述:

已知3x+y+2z=28,5x-3y+z=7,求x+y+z的值

经过非常仔细的观察后发现:
x+y+z=4/7(3x+y+2z)-1/7(5x-3y+z)
=15