In the given figure, sides 
and 
of cyclic quadrilateral 
are produced to 
and 
respectively.
If 
and 
find the value of 
∠ABC + ∠CBF = 180°[Because ABF is a straight line]
⇒ ∠ABC + 130° = 180°
⇒ ∠ABC = 50°
∴ x = ∠ABC = 50°[Exterior angle = interior opposite angle]
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