Question

How do I solve for y?

Answer 1

Short Answer: y = 36°
Remark
What an interesting question!! The first thing you have to do is find out what the interior angle of a regular pentagon is. After you have done that, you can calculate y.

Method.
The exterior angles of a regular figure add up to 360°. 

Step One
Find out the size of the exterior angles of a  regular pentagon. 
There are 5 such angles. They add up to 360°

5x = 360  Divide by 5
x = 360 / 5
x = 72°

Step Two
Find out the value of the interior angles of a pentagon.

Method
The interior and exterior angles add up to 180°
Exterior Angle + Interior Angle = 180°
Exterior angle = 72 degrees
72° + Interior Angle = 180°                  Subtract 72 from both sides.
Interior Angle = 180° - 72° 
Interior Angle = 108°

Step Three
Solve for y.

There are 3 tiles each with an angle of 108° that are placed together. So y + 3 interior angles = 360°

y + 3*interior angles = 360°
y + 3*108 = 360 
y + 324 = 360 Subtract 324 from both sides.
y = 360 - 324
y = 36°