Angle Sum Theorem, thank you so much for the help, in advance!

[tex]y + x = 180° \\ \Leftrightarrow y = 180° - x = 180° - (180° - 30° - 25°) = 30° + 25° = 55°[/tex]
sum of the 3 angles of a triangle = 180°
x +25+30 = 180°
x = 180- 55 = 125°
Now angle x + angle y = 180°( supplementary angle)
so put the value of x in the equation, we have
125 + y = 180°
y = 180 -125
y = 55°