根据题意得:2x-y+1=0x-2=0,
解得:x=2y=5,
则x+y=2+5=7.
故答案是:7.
We like ______ on Sundays when the whole family get together talking and laughing. [ ]
A. this
B. that
C. it
D. those
一个关系中属性个数为1时,称此关系为
A.对应关系
B.单一关系
C.一元关系
D.二元关系