Answer: The value of y is 135 degrees
Step-by-step explanation: Please refer to the attached picture for details. The sum of angles on a straight line equals 180 degrees.
If a line comes out of another line then it would divide it into two separate angles (still on the same line).
One of the angles has been identified as 45 degrees, that means the other angle can be calculated as follows;
Angle y + 45 = 180 {Sum of angles on a straight line equals 180}
Subtract 45 from both sides of the equation
Angle y = 135 degrees