Solution:
We know that:
[tex]1. \space\ r + s + t = 180 + 180 + 180 - (Sum \space\ of \space\ interior \space\ angles \space\ of \space\ a \space\ triangle)\\ \\ 2. \space\ Sum \space\ of \space\ interior \space\ angles \space\ of \space\ a \space\ triangle = 180[/tex]
This means that:
[tex]1. \space\ r + s + t = 180 + 180 + 180 - (180)[/tex]
Let's simplify the equation to find r + s + t.
Simplifying the equation:
[tex]r + s + t = 180 + 180 + 180 - (180) \\ \\ r + s + t = 180 + 180 + 180 - 180 \\ \\ r + s + t = 180 + 180 \\ \\ r + s + t = 360[/tex]
Thus, the sum of r, s and t is 360°
