Question 884531
(5x+4y=12)3=>15x+12y=36
(7x-6y=40)2=>14x-12y=80
by adding two equations, we get
29x=116
=>x=4
and 
  5(4)+4y=12
=>4y=12-20
=>4y=-8
=>y=-2
(x,y)=(4,-2)