Step-by-step explanation:
since we have at F a 90 degree angle, b is simply the difference between 90 and 33 degrees
b = 90 - 33 = 57 degrees.
and since all angles in a triangle must sum up to 180 degrees, this applies also to HFG. and we know 2 angles : H = 54 degrees, b = 57 degrees
a = 180 - 54 - 57 = 69 degrees
e is simply the counterpart of the 90 degree angle at F, as these 2 angles must sum up to 180 degrees again.
so, e = 180 - 90 = 90 degrees.
c is the complementary angle to 54, as for a pair of angles at a line intersection, these 2 angles must again sin up to 180 degrees
c = 180 - 54 = 126 degrees
and d is the third angle of EFG, where we know 2 angles, and again, the sum of all angles must be 180.
d = 180 - 90 - 69 = 21 degrees
