X+Y+Z=15 X+5Y+10Z=70
5个回答

两式相加10X+5Y+Z+X+Y+Z=70+15

11X+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代入10X+5Y+Z=70,得10X+5Y+5=70,10X+5Y=65

由X+Y=10,得5X+5Y=50

10X+5Y=65,5X+5Y=50两式相减得5X=15,X=3

X+Y=10,Y=7

所以X=3,Y=7,Z=5