x° and 25° make up a 90° angle, so you can do:
x° + 25° = 90° Subtract 25 on both sides
x = 65°
A straight line is 180°, so you could do:
x° + 25° + 65° + y° = 180°
Since you know "x", you can plug it in
65° + 25° + 65° + y° = 180°
155° + y° = 180°
y° = 25°
