Using the substitution method:
{ x = 4 - 2 y
4 x + 8y = 20
Subsititute x = 4 - 2 y
[ 4(4 - 2 y ) + 8y = 20 ]
Refine:
4( 4-2y ) + 8y = 20
16 - 8 y + 8 y = 20
0 = 16 - 20
-4 = 0
-4 = 0
-4 = 0 ( is false , therefore the system of equations has no solution )
hope this helps!