Found the answer. It's just a bunch of trigonometry, and I'll try to visualize it with a blender model here right quick.
In this problem, you're basically going to find the lengths of the red, blue, and yellow lines, and add these lengths to the X, Y, and Z of point A, respectively, to get the position of point B. The large light-green semicircle represents our yaw.
The angle between the green and purple lines is our pitch, 89.193 degrees. The length of the green line is the given distance from point A to point B, 88.87. Using this information, we can find the length of the yellow and purple lines.
The yellow line is opposite to the green-purple angle, and according to "SOH CAH TOA", we can use sine to find the length of the yellow line using our pitch, and the length between the two points as the hypotenuse of the triangle.
sin(89.193) = yellow / 88.87
yellow = sin(89.193) * 88.87
yellow = 88.861In order to find the lengths of the red and blue lines, we need the length of the purple line. The length of the purple line is found easily, again, using the distance between A and B as the hypotenuse. It is adjacent to the angle, so we use cosine.
cos(89.193) = purple / 88.87
purple = cos(89.193) * 88.87
purple = 1.252Keep in mind, the pitch is almost 90 degrees and points straight up, therefore the purple, blue, and red lines aren't going to be very long at all.
Now we use the length of the purple line, and our yaw to calculate the lengths of red and blue.
cos(123.525) = red / 1.252
red = cos(123.525) * 1.252
red = -0.691
sin(123.525) = blue / 1.252
blue = sin(123.525) * 1.252
blue = 1.043
Red is negative, because our yaw crosses the x axis, and therefore, we must subtract from point A instead of add.
Now we have our offsets, and the last thing we need to do is simply add them to point A to get point B:
bX = 271.617 - 0.691 = 270.926
bY = -28.875 + 1.043 = -27.832
bZ = 12,255.698 + 88.861 = 12344.559
Point B is at (270.926, -27.832, 12344.559).
