in triangle HBC , angle H is also 48 degree degree since the line is parallel the connection between angle H and angle A is alternate interior angle and alternate interior angle are always equal.
so angle H = 48 degree
in triangle HBC
angle H + angle C = angle ABC (sum of two interior opposite angles are equal to the exterior angle formed)
One polynomial identity that crops up often in various areas is the difference of squares identity: A2-b2=(a-b) (a+b) We meet this in the context of rationalising denominators.
