how do you do this

2x+9y=4

2x-6y=-1     multiply this equation by - 1   = -2x + 6y = 1

So we have

 2x +9y=4

-2x +6y=1    now.....add these together

      15y = 5        divide both sides by 15

y = 5/15 = 1/3

And using the frist equation, we can find x  by substituting 1/3 for y

2x + 9(1/3)  = 4

2x + 3  = 4    subtract 3 from both sides

2x  = 1          divide by 2  on both sides

x = 1/2

So the solution is (x, y) = (1/2, 1/3)