Because F and C are consecutive angles, they add up to 180°. So 180-105=75. Angle C is 75, which makes B wrong. After finding that C is 75°, then you use the verticle angles theorem to show that angle A is 75°. Hope this helps you.
This is for the first graph because if you look at the bottom half of a circle is 180 so since one is 121 you just have to subtract 121 from 180 and you have your answer
