Answer:
A= 69 degrees
Step-by-step explanation:
if all those angles equal a total of 180 degrees then all you need to do is add the angles your given which in this case is 21 and a 90 degree angle which would equal 111 degrees, then subtract 111 from 180 and that would be the answer to the missing angle, which is 69 degrees.
21 + 90 = 111
180- 111 = 69
