Question

a+b=75+b+c=85+a+c=80求a+b+c等于多少

Answer 1

由式子a+b=75+b+c可得a-c=75①
由式子85+a+c=80可得a+c=-5②
由①+②得2a=70解得a=35带入①式得c=-40
由式子75+b+c=85+a+c解得b=45
最后求得a+b+c=35+45-40=40

Answer 2

a+b=75+b+c=85+a+c=80
可写成
a+b=80,①
b+c=5,②
a+c=-5,③
(①+②+③)/2,得a+b+c=40.

Answer 3

85+a+c=80
a+c=-5①
75+b+c=85+a+c
b-a=10②
a+b=75+b+c
a-c=75③
①+③=2a=70
a=35
②+③=b-c=85
①+②=b+c=5
2b=90
b=45
c=-40
a+b+c=35+45-40=40
望采纳，谢谢！

Answer 4

（a+b）+（75+b+c）+（85+a+c）=80+80+80
2a+2b+2c+75+85=240
2(a+b+c)=80
a+b+c=40