Question 1077715
This is a right triangle with legs 15 and 21.  The hypotenuse or c, is sqrt (225+441)=sqrt(666)=25.81.
can use Law of Sines
25.81/sin C=25.81= a/sin A=15/sin A; sin A=15/25.81=0.5812.  Take the arc sin (0.5812)=35.53 deg angle A
21/25.81=0.8136; arc sin (0.8136)=54.45 deg angle B