13 - (x+2) = 8
subtract 13 from both sides
-(x+2) = -5
divide by -1 to get rid of negative
(x+2) = 5
subtract 2 from both sides
x=3
The standard forrm equation of the circle is (x-h)² + (y-k)² = r²
where h,k : x,y-coordinate of the center
r : radius of the circle
Get the center of the circle : h = (x1 + x2)/2 = (9+5)/2 = 7
k = (y1 + y2)/2 = (4+2)/2 = 3
=> the center is (7,3)
Because the given information gave 2 endpoints so we can choose one of these, then use the distance formula to get the radius
r = √(x1 - h)² + (y1 - k)²
r = √(9 - 7)² + (4 - 3)²
r = √2² + 1²
r = √5
Finally, the equation of the circle is (x - 7)² + (y - 3)² = (√5)²
(x - 7)² + (y - 3)² = 5
If the first one is a = 180 - b, and not 180 - 6, then that is correct.
Also, 360 = 2a + 2b is correct
It is in the attachment.
Let me know if this helps.
also let me know if it shows up for you and if it don't ill post your answer in the comments.