Answer:
y = A ([tex]6\sqrt{3}[/tex])
Step-by-step explanation:
[tex]x^{2} +y^{2} = 12^{2}=144\\y^{2}-9^{2}=x^{2} -3^{2} \\x^{2} -y^{2}=-72\\2y^{2}=216\\y^{2}=108\\ y=\sqrt{108}=6\sqrt{3}[/tex]
