Răspuns :
90+21+75=186
2a+2b+2c=186
2•(a+b+c)=186
a+b+c=186:2=93
93:3=31
a=31
b=31
c=31
proba:2•31+2•31+2•31=186
2a+2b+2c=186
2•(a+b+c)=186
a+b+c=186:2=93
93:3=31
a=31
b=31
c=31
proba:2•31+2•31+2•31=186
1) a+b=70( relatia 1)
b+c=21(relatia 2)
a+c=75(relatia 3)
(+) -aduni cele 3 relatii=>
2(a+b+c)= 166 =>
a+b+c=83(relatia 4)
Din (4) - (1) => c=13
Din(4) - (2) => a=62
Din (4) -(3) => b=8