To find the value of angle A, we'll need to use a trigonometric function. In this case, we are given the adjacent side and the hypotenuse. So, we should use cosine. And because we are finding an angle, we will need to use the inverse cosine.
cos(a) = 3/8
a = cos^-1(3/8)
a = 67.98 degrees
Hope this helps! :)