algebra- simultaneous equations- I need help

x^2+y^2=30; x+2y=7

x=7-2y

x^2 +y^2=30

(7-2y)^2+y^2=30

5y^2?28y+19=0

use quadratic formula to get

y=(28+sqrt(28^2-4(5)(19)))/(2(5), y=(28-sqrt(28^2-4(5)(19)))/(2(5)

then plug into x+2y=7 to find x