When you do the substitution method, you would have the x and y variables equal to zero. In systems of equations, the equations are equal with each other.
20x-8y=-5 10x-4y=-4
20x-8y=-5 -2(10x-4y=-4)
20x-8y=-5 -20x+8y=8
The 20x and -20x cancel out The -8y and 8y also cancel out. Thus leaving -5 and 8
According to system of equations, the equations must be equal. Additionally, -5 does not equal to 8.
