Question

What is the value of x?
x = ___°

Answer 1

I believe the answer to be 45
Hope this helps you 

Answer 2

All of the angles must add up to 180 degrees, since the sum of all the interior angles in a triangle is always 180 degrees.

x + 80 + 55 = 180

Add 80 and 55

x + 135 = 180

Subtract both sides by 135

x = 45

That's your answer.

Have an awesome day! :)