Question

How do I solve for x in the two equations below using substitution.
4x-2y=4
8x+2y=20

Answer 1

4x-2y=4
8x+2y=20

12x=24
x=24/12
x=2

sub x into 8x+2y=20
8(2)+2y=20
16+2y=20
2y=20-16
2y=4
y=4/2
y=2

solution (2,2)

check
4x-2y=4(2)-2(2)=4
8x+2y=8(2)+2(2)=16

hope this helps

Answer 2

`4x-2y=4 \\ 8x+2y=20 \\ \\ \hbox{from the 1st equation:} \\ 4x-2y=4 \\ -2y=-4x+4 \\ y=2x-2 \\ \\ \hbox{substitute 2x-2 for y in the 2nd equation:} \\ 8x+2(2x-2)=20 \\ 8x+4x-4=20 \\ 12x=24 \\ x=2 \\ \\ y=2 \cdot 2-2 \\\ y=4-2 \\ y=2 \\ \\ \hbox{the answer:} \\ x=2 \\ y=2`