Since the cosine ratio involves adjacent/hypotenuse, we can see that the adjacent side is 9 and the hypotenuse is 41. For angle B, the adjacent side is the leg closest to the angle in question. So that would be side AB.
Therefore, AB = 9 and BC = 41 are the adjacent and hypotenuse for reference angle B.
Apply the pythagorean theorem to solve 9^2+x^2 = 41^2, and you should get x = 40. This is the other leg of the triangle. Or you could note how tan(C) = 9/40 to imply that AC = 40 is the adjacent side for reference angle C.
