Answer:
(x - 5)² + (y + 7)² = 81
Step-by-step explanation:
The equation of a circle in standard form is
(x - h)² + (y - k)² = r²
where (h, k) are the coordinates of the centre and r is the radius
Here (h, k) = (5, - 7) and r = 9, thus
(x - 5)² + (y - (- 7))² = 9², that is
(x - 5)² + (y + 7)² = 81 ← equation of circle
Let S be the number of Brand S snowboards sold.
Let B be the number of Brand B snowboards sold.
309S + 489B = 4299
S + B = 11
S = 6 snowboards sold
B = 5 snowboards sold
The angle does not matter. Think of it as finding the other side to a triangle. Use

a=39 (line AB)
b=b (the leg we need to find)
c=89 (line BD)


(subtract the 1521 from both sides)

(square root both sides)

b = 80
AD=80