A system of linear equations solved by elimination means that you have to figure out a way to eliminate one of the variables so that you can solve for the other one.
Here, you could multiply both sides of the top equation by 2 to get:
2 * (-9x + 2y) = -1 * 2
-18x + 4y = -2
Now line this up with the bottom equation:
-18x + 4y = -2
18x - 7y = 17
We see that if we add the two equations together, we can get rid of the x variable:
4y + -7y = -2 + 17
-3y = 15
y = -5
If we know y, we can use it to find x:
-9x + 2 * -5 = -1
-9x - 10 = -1
Add 10 to both sides:
-9x = 9
Divide both sides by -9:
x = -1
So, the answer is x = -1 and y = -5
