Given the system of equations
3x - 4y = -4
5x - 4y = 12
To eliminate any of the variables, the important point to note is that the coefficients of the variables to be eliminated should be the same and maybe opposite in sign
In the equations, y in both equations have the same coefficient (4). So any of the equation can be multiplied by 1 or -1
If one of the equation is multiplied by, then we will subtract the result obtained from the other equation, whereas if one of the equation is multiplied by -1, we will simply add the result to the other equation