X+Y=Z

问题描述:

X+Y=Z
5X+5Z=80
3Y+5Z=70
XYZ是等于几?

X+Y=Z (1)
5X+5Z=80 (2)
3Y+5Z=70 (3)
(2)-(3)
5X-3Y=10 (4)
(1)*5+(2)
5X+5Y+5X+5Z=5Z+80
10X+5Y=80
2X+Y=16 (5)
(4)+(3)*3
5X-3Y+6X+3Y=10+48
11X=58
X=58/11
Y=16-2X=60/11
Z=X+Y=118/11