To put an equation in slope intercept form, clear or solve the equation for y.
This way:
[tex]\begin{gathered} -4x+y=6 \\ y=4x+6 \end{gathered}[/tex]
The first equation in slope intercept form is y = 4x + 6.
Once done this step, solve the system by using substitution.
Replace the expression found above for y in the second equation and solve for x.
[tex]\begin{gathered} -5x-y=21 \\ -5x-(4x+6)=21 \\ -5x-4x-6=21 \\ -9x=21+6 \\ -9x=27 \\ x=\frac{27}{-9} \\ x=-3 \end{gathered}[/tex]
Using this value of x, found the value of y by replacing x on the equation in slope intercept form.
[tex]\begin{gathered} y=4x+6 \\ y=4(-3)+6 \\ y=-12+6 \\ y=-6 \end{gathered}[/tex]
The solution of this system is x=-1 and y=-6.
