The problem asks to find the value of $y$, where $y$ is the obtuse angle formed by two intersecting lines, and the acute angle between these lines is given as $45^{\circ}$.

1. Problem Description

The problem asks to find the value of $y$, where $y$ is the obtuse angle formed by two intersecting lines, and the acute angle between these lines is given as $45^{\circ}$.

2. Solution Steps

The sum of angles on a straight line is $180^{\circ}$. The obtuse angle $y$ and the acute angle $45^{\circ}$ form a straight line. Therefore, we can write the equation:

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

Subtract $45^{\circ}$ from both sides:

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

$y = 135^{\circ}$

3. Final Answer

$y = 135^{\circ}$