Answer:
x = 75°
Explanation:
The angle at the centre is twice the angle on the circle subtended on the same arc.
The angle at the centre is
360° - (285 - x)
= 360 - 285 + x
= 75 + x
Thus
x =
(75 + x) ← multiply both sides by 2 to clear the fraction
2x = 75 + x ( subtract x from both sides )
x = 75°