Not positive for what you are looking here....
4x + 3y = -1 multiply both sides of equation by 3 12x + 9y = -3
3x -4y = -7 multiply both sides oe eqaution by -4 -12x+16y = 28
Now add the two red equations
25y = 25
y = 1 NOW, use this value of y in any of the equations to calculate the value of 'x' ......