Răspuns :
X+3Y=10
2Y+5Z=149
X+7Y+10Z=?
2Y+5Z=149 | *2
4Y+10Z=298
X+3Y=10
-------------------adunam cele doua ecuatii
X+7Y+10Z=308
2Y+5Z=149
X+7Y+10Z=?
2Y+5Z=149 | *2
4Y+10Z=298
X+3Y=10
-------------------adunam cele doua ecuatii
X+7Y+10Z=308