2x+4y=450
2x=450-4y
x=450-4y÷2----- equation 1
4x+2y=420
4x=420-2y
x=420-2y÷4----- equation 2
putting the value of x in equation 1
x=450-4y÷2
420-2y÷4=450-4y÷2
2(420-2y)=4(450-4y)
840-4y=1800-16y
840-1800=-16y-4y
-960= -12y
y=80
putting the value of y in equation1
2x+4y=450
2x+4×80=450
2x+320=450
2x=450-320
2x=130
x=130÷2
x=65
the value of x is 65 and y is 80