Răspunsuri

2014-10-13T19:57:15+03:00
2a + b +2c=42
a + 2b + c= 51
-------------------
3a+3b+3c=42+51
3(a+b+c)=93
a+b+c=93:3
a+b+c=31

de ce 3 ?
a adunat cele 2 propozitii, adica 2a+b+2c+a+2b+c=42+51
si ai 2a+a+2b+b+2c+c=42+51