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x+y=10 y+3z=26 calculati 2x+5y+9z

Răspuns :

2(x+y)=20
2x+2y=20

3(y+3z)=78
3y+9z=78

2x+2y+3y+9z=78+20
2x+5y+9z=98
x+y +x+y+y+3z+y+3z+y+3z=10+10+26+26+26=98