7x+3y+z=316.
10x+4y+z=420.
-得:
3x+y=104.
*3得
9x+3y=312.
-得:
x+y+z=108 7x+3y+z=316.
10x+4y+z=420.
-得:
3x+y=104.
*3得
9x+3y=312.
-得:
x+y+z=108