10X+5Y+Z=70 X+Y+Z=15
问题描述：
10X+5Y+Z=70 X+Y+Z=15
10X+5Y+Z=70
X+Y+Z=15
答
两式相加10X+5Y+Z+X+Y+Z=70+1511X+6Y+2Z=85两式相减(10X+5Y+Z)-(X+Y+Z)=70-15 9X+4Y=65所得两式相减(11X+6Y+2Z)-(9X+4Y)=85-65 2X+2Y=20 X+Y=10代入X+Y+Z=15,所以Z=5把Z=5...