x=35-y.
70-2y+3y=90. y=20
x=35-20=15
Bună!
[tex]\left \{ {{x+y=35/*(-2)} \atop {2x+3y=90}} \right. => \left \{ {{-2x-2y=-70} \atop {2x+3y=90}} \right.[/tex]
_________ (+)
/ y=20
x+y=35 ⇔ x+20=35 ⇒ x=15
