We have an angle of $45^\circ$. We are looking for the supplementary angle $y$ such that the sum of the two angles is $180^\circ$.

1. Problem Description

We have an angle of $45^\circ$. We are looking for the supplementary angle $y$ such that the sum of the two angles is $180^\circ$.

2. Solution Steps

Supplementary angles add up to $180^\circ$. Therefore, to find the value of $y$, we can use the following formula:

$y + 45^\circ = 180^\circ$

Subtract $45^\circ$ from both sides:

$y = 180^\circ - 45^\circ$

$y = 135^\circ$

3. Final Answer

$y = 135^\circ$