Answer:
Option B. 67.6°
Explanation:
In the given triangle ABC angle C is the right angle, side AB = 21 and side AC = 8.
We have to find the measurement of angle A.
Now from cosine rule we can write

Here Base in the corresponding side of the angle A that is 8 and hypotenuse is 21.
Now we put the values
Cos x = 8/21 = 0.3809

Or x = 67.61°
Therefore measurement of angle A or x = 67.6° is the answer.