Answer:
t, r, s
Explanation:
The sum of angles is 180°, so you have ...
(x +28) + (2x +16) + (x +12) = 180
4x + 56 = 180
4x = 124
x = 31
For this value of x, ...
2x+16 > x+28, so S is the largest angle and "s" is the longest side.
x +12 < x +28, so T is the smallest angle and "t" is the shortest side.
The sides, shortest to longest, are ... t = RS, r = ST, s = RT.