The triangle is formed by using the diameter as its base, so angle opposite to the diameter, i.e., ∠QRS = 90°
Given that QR and SR are equal, so it is an isosceles triangle. Hence, ∠RQS and ∠RSQ are equal. Hence, ∠RSQ = x + 6° because given that ∠RQS = x + 6°.
We know that all angles of a triangle adds up to 180°.
So, (x+6°) + (x+6°) + 90° = 180°
=> 2(x+6°) + 90° = 180°
=> 2(x+6°) = 180° - 90°
=> 2(x+6°) = 90°
=> 2x + 12° = 90°
=> 2x = 90° - 12°
=> 2x = 78°
=> x = 78°/2
=> x = 39°
