Answer:
just look at the algebra formula and simplify to get your answer. Remember to use your powers well
Answer: 
Step-by-step explanation:
x^2+y^2=r^2 --> subtract x^2 to other side
y^2=r^2-x^2 --> square root both sides
y=sqrt(r^2-x^2)
Do u still need the answer its been a week now!
I am pretty sure your answer is going to be 243
I hope this helps, and good luck!!