Explanation:
a = 72°, alternate interior angle to the one marked 72°, so congruent
b = d = j = 180° -2(72°) = 36°; twice angle 'a' is supplementary to b; all the acute angles where parallel lines are crossed are the same measure
c = e = h = 2(72°) = 144°; the obtuse angles where parallel lines are all the same measure
f = (180° -e)/2 = 18°, base angle of isosceles triangle
g = 180° -f = 162° . . . supplementary to the base angle
k = 54°, complementary to b
m = 126°, supplementary to the base angle of the triangle containing 'a'.
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Additional comment
The base angles of an isosceles triangle with third angle A are ...
B = C = (180° -A)/2
Angles that together make a straight line have a total of 180°.
