Rearrage so you have x+3=y, and x2 +y2 =9. Substitute the equation into another so you have x2+(x+3)2=9. Expand the brackets so that you have x2+x
Both equations should be given with variables of y and x. They may however not be given in the form y=mx+c where m and c are constants, the equation could be given in the form of a circle (y-a)2