Răspuns:
a) aducem la acelasi numitor (inmultim cu 2 fiecare ecuatie)
x+5y=8
7x-y=20 => y=7x-20
x+35x-100=8 36x=108 => x=3 y=21-20=1 y=1
b) aducem la acelasi numitor
3x-y+2x=0 => y= 5x
2x-y+3y=12
2x-5x+15x=12 12x=12=> x=1
y=5*1=5 y=5
