To solve this answer, you must understand the side ratios that come with special right triangles.
There are 2 special right triangles, both identified by their angles.
- 45-45-90 triangles
 - 30-60-90 triangles
 
Both triangles come with side ratios.
30-60-90 triangles have side ratios of x:x
:2x
45-45-90 triangles have side ratios of x:x:x

The triangle in this question is a 45-45-90 triangle meaning the side ratios follow the x:x:x
 format.
You have been given the side length of 6
As the side with the length of 6 is across the angle 45°, then this angle is one of the x's in the ratio x:x:x
 
The next 45° angle is facing y, meaning that side also has the length of 6.
To find x, you can just plug in x into x
, leaving you with the side length 
6

Your angle lengths are 6,6 and 6
