Respuesta :

Angle TRS is equal to 180 - 9x (straight angles).  

The sum of all the interior angles of a triangle is 180.  Thus,

180 - 9x + 5x + 9 + x = 180, resulting in -9x + 5x + 9 + x = 0. 
Then -4x + x = -9, or -3x = -9, or x = 3 (answer)