Respuesta :

nobillionaireNobley
a = 90 + 72 = 162 degrees
b = 180 - 162 = 18 degrees.
Kunchan
Total value of the inner angle is 180
So
b + 90 + 72 = 180
b = 180 - 162
b = 18

But 
a + b = 180
a + 18 = 180
a = 162