Can someone please help me with this question, I have multiple of them and have no idea where to start. If you can help me with this please show how you got it because im clueless

Answer:
Step-by-step explanation:
( 3x - 7 )° + ( 9x - 2 )° + ( x + 7 )° = 180°
13x = 182
x = 14
m ∠ A = ( 3 × 14 - 7 )° = 35°
m ∠ B = ( 9 × 14 - 2 )° = 124°
m ∠ C = ( 14 + 7 )° = 21°