Since the two angles \( x \) and \( y \) are on a straight line, they are supplementary angles. This means that they add up to \( 180^\circ \).
Given that \( x = 125^\circ \), we can find \( y \) using the following equation:
\[ x + y = 180^\circ \]
Substituting the value of \( x \):
\[ 125^\circ + y = 180^\circ \]
To find \( y \), subtract \( 125^\circ \) from both sides:
\[ y = 180^\circ - 125^\circ \]
\[ y = 55^\circ \]
Therefore, the value of \( y \) is \( 55^\circ \).
The correct response is:
55°