To find the diameter of a circle, using only the circumference, you need to divide the circumference by π, or 3.14.
So in this case, you must divide 12 by 3.14, which gives you 3.82.
I even double checked this, and should be correct then.
If this an angle on a straight line the answer is k=73°
Answer:
Bottom left
< means that it's dashed line