First let's take our two given equations
-2x-9y=-25
-4x-9y=-23
Now we need to cancel out either x or y by making them the same values, but opposite on being negative or positive
We do this by multiplying the entire equation by a number
-1(-4x-9y=-23)=4x+9y=23
Now we have a new equation
-2x-9y=-25
4x+9y=23
Combine the two equations and your y will cancel out
2x=-2
Now we need to find x
2x=-2
Divide by 2 on each side
x=-1
Now we need to plugin our x to find the y by plugging the x into any of the first given equations
-2(-1)-9y=-25
2-9y=-25
-2 -2
-9y=-27
Divide by -9 on each side
y=3
x=-1, y=3