Răspunsuri

2014-10-02T22:09:54+03:00
3a+3b+4b+4c=3(a+b)+4(b+c)=3x20+4x30=60+120=180
Cel mai inteligent răspuns!
2014-10-02T22:13:46+03:00
A+b=20=>a=20-b
b+c=30=>c=30-b=>b=30-c

3xa+7xb+4xc= 3 x(20-b)+7xb+4x(30-b)
60-3b+7b+120-4b=180-+4b-4b=180

1 5 1