已知x+y=3,y+z=4,x+z=5,则x+y+z等于( ) A.6 B.8 C.10 D.12
问题描述:
已知x+y=3,y+z=4,x+z=5,则x+y+z等于( )
A. 6
B. 8
C. 10
D. 12
答
由题意得:
x+y=3① y+z=4② x+z=5③
①+②+③得:2x+2y+2z=12,
即x+y+z=5.
故选A.