I think it is 555??
355+200=555
54=.9x Solve for x. x=54/.9=60
You are right. In circle equation we have =r² so the correct answer will be C od D. But we have to calculate the center of a circle.

Complete the square:

And we have:

So the answer is C (the same left side of equation).
i belive 60% becuse it lands on heads 60 time out of a hudred