Answer:
∠ R = 90°
Step-by-step explanation:
The sum of the 3 angles in a triangle = 180° , that is
∠ R + ∠ S + ∠ T = 180° , substitute values
∠ R + 29° + 61° = 180°
∠ R + 90° = 180° ( subtract 90° from both sides )
