Since angle a is 30 degrees and that it’s a right triangle, you know it’s a 30-90-60 triangle.
16. Angle b is 60 degrees. Because the interior angles of a triangle always add up to 180, and you have 90 and 30 degrees already, 180-120 is 60 degrees
17. Side a is 21.65. Since the characteristics of a 30-90-60 triangle is that the long leg is the square root of 3 times a, and the hypotenuse is 2a, 25/2 is 12.5, and when multiplied by the square root of 3 is approximately 21.65
18. Side b is 12.5 because it’s the short leg and is equal to a which would be 12.5
19. The area for the triangle is approx 135.32 which is side a times side b divided in half