Answer:
∠ S = 33°
Step-by-step explanation:
TS is a diameter of the circle , then
∠ R = 90° ( angle in a semicircle )
The sum of the 3 angles in Δ RST is 180° , that is
∠ R + ∠ S + ∠ T = 180° ( substitute values )
90° + ∠ S + 57° = 180°
∠ S + 147° = 180° ( subtract 147° from both sides )
∠ S = 33°
