I don’t understand how to really do this

Answer:
The answer would be D, or m angle A = 55 degrees.
Step-by-step explanation:
This angle complements the other 55 degree angle below it.
As for the other options, keep in mind that a straight line equals 180 degrees. Using the complementary angles, we can infer that angle B is equivalent to 55 degrees and and angle C is equivalent to 60 degrees. I got angle B by subtracting 60 and 65 from 180, giving me 55.
I hope that makes sense!