Okay, here's your rough calculation, but you should pay me at least half what you paid the surveyor. I'll take the drawing to mean that east and west are parallel to the horizontal members (North is up!). Obviously, this is not the case for the real world, but it will do.
We are totally in luck that the horizontal members appear to be parallel. This simplifies the task considerably.
Starting on the left of your drawing and using the bearings provided, that SW angle is 87.32º.
Walking east until the NW corner is directly above you, we manage to move only 14.174 ft.
If we then connect this point to the NW Corner, we find this distance to be 302.80 ft.
The trick is, then, to draw another line, parallel to the one we just drew, but farther to the East, so that we contain 1/3 of your 5.181 acres.
A little algebra: 302.80\cdot\frac{n + (n+14.174)}{2} = 75228 \implies n = 241.35 ft
In other words, if you start at the NW Corner, and mark off 241 ft toward the road, then make a right turn (90º) to the southern boundary, you will have marked off very close to 1/3 of the land.
If we do this again, from the line just established, it is easier because it is rectangular and not trapezoidal. In this case, 302.80\cdot m = 75228 \implies m = 248.44 ft. This should be a little more because you don't have that odd little triangle on the West end.
With a little luck, 829.25 - 241.35 - 248.44 = 339.46 is your answer. I'm a little worried that this is so close to the drainage ditch, but you're not paying me enough to spend any more time on this. Suffice it to say that if 339½ ft from the road puts you West of the drainage ditch, you're good. You will have to figure out how to make right angles since I mostly mentioned measurements along the Northern boundary. Translating them to the Southern boundary can be accomplished a couple of ways.
Well, good luck with that. I was just in Wyoming, but we mostly stayed on I-80.
