Less than right? Because it’s a negative?
Answer:

Step-by-step explanation:
A circle centered at (0,0) with radius r is 
Since your circle has diameter of 12, then its radius is 6. Then 
So a possible answer is: 
If you want to move the location of the center, but keep it on the x-axis, then add or subtract a number to the x, such as this:

The center of this circle would be (-4, 0) which is still on the x-axis.
The answer to that question is 250.
X+x+4+3x-9=90
5x-5=90
+5 +5
5x=95
5x/5=95/5
x=19