a+b+c=71 a-gaini b=gaste c=oi
2 x a +2 x b + 4 x c= 172 2a+2b+4c=172
a= 3 x b
Din prima ecuatie c= 71-a-b c=71- (3xb)-b c= 71 - 3xb-b c=71-4b Inlocuiesc in ecuatia 2 pe a si c 2 x 3b + 2b + 4(71-4b) = 172 6b+2b-16b+284=172 8b=284-172 8b=112
b=112:8 b=14 gaste a=3b a=3 x 14 a=42 gaini c=71-4b c=71-4 x 14 c=71-56
c=15 oi