2x+3y=9/×4
5x-4y=7 /×3
8x+12y=36
15x-12y=21
------------------+(le aduni)
8x+15x+12y-12y=36+21
23x=57
x=57/23
revii la una dintre relatii si il inlocuiesti pe x
8x+12y=36
8×57/23+12y=36
456/23+12y=36
12y=36-456/23
(aduci la acelasi numitor)
12y=828/23-456/23
12y=372/23
y=372/23÷12
y=372/23×1/12
y=372/276
y=31/23
