(-5,5)
1) Let's solve this by the Elimination/Addition Method
8x+9y=5
-4x-y= 15 Multiply the whole equation by 2, to eliminate x
8x+9y=5
-8x-2y= 30 Add both equations simultaneously
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7y = 35 Divide both by 7
y=5
2) Now, we can plug that y=5 into the simplest equation. For convenience. let's pick
-4x -y= 15
-4x -5 = 15 Add 5 to both sides
-4x = 20 Divide both sides by -4
x = -5
3) Then the solution to this Linear System is (-5,5)