Answer:
∠ R 
 90°


 
Explanation:
Given that in triangle RST 

Now as per condition one angle is greater than sum of other two angles.
Since in triangle ,sum of all three angles = 180°
Hence if one angle is 90° then sum of other two must be equal to 90° 
And if one angle is 90° then only other two angle be 45° each 
Here Let if angle s = angle T = 30° then with this condition angle r is 120° , which is greater than 90°
So, from above it conclude that 
For , 

∵ ∠ R = 120° , then it is greater than 90°
I.e ,  ∠ R 
 90°


  Answer