What is the value of x?

The letter "x" is often used in algebra to mean a value that is not yet known. It is called a "variable" or sometimes an "unknown". In x + 2 = 7, x is a variable, but we can work out its value if we try! A variable doesn't have to be "x", it could be "y", "w" or any letter, name or symbol

x = 96 degree.

Step-by-step explanation:

G interior angle = 180 - (45 + 53) = 84  

As all angles in a triangle add up to 180 degree.

G exterior angle = 180- 84 = 96 degree

x = 96

As all angles on a straight line add up to 180 degree.