What choice of answers do you have?
Answer:
15/4 and 45/4
Step-by-step explanation:
Let x and y be the numbers
x = 3y
x+ y = 15
Substitute the first equation in to the second equation
3y+y = 15
4y = 15
y = 15/4
x = 3(15/4)
x = 45/4
The two numbers are 15/4 and 45/4
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).