The given system of equations is expressed as
5x + 4y = -30
3x - 9y = -18
To solve for x and y by elimination, the first step is is to make the coefficient of either x or y in both equations to be equal. If we decide to make the coefficient of x to be equal, we would multiply the first equation by 3 and the second equation by 5. Thus, we have
15x + 12y = - 90
15x - 45y = - 90
We would eliminate x by subtracting the last equation from the one on top. It becomes
15x - 15x + 12y - - 45y = - 90 - - 90
0 + 57y = 0
57y = 0
y = 0/57 = 0
Substituting y = 0 into 5x + 4y = -30, we have
5x + 4 * 0 = -30
5x = - 30
x = - 30/6
x = - 6