Hello all. I am a little shy about asking this question because it exposes my lack of math/geometry knowledge and my inexperience with the array of tools in ArcMap. I am familiar with only a narrow set of them in the parcel fabric. Also, I use ArcMap 10.5.1.
Some context about my needs as a tax parcel cartographer: Many tax parcels are lots that have been formally platted out in subdivisions. The officially recorded plat has measurements and acreages. In a given section of land, some of the land may be platted out and some may not. The unplatted land is assumed to have measurements and acreages calculated from the remainder of a standard size section with the platted measurements and acreages taken out. We call those "balance parcels." Often, I find myself needing to verify the acreage of a balance parcel by gathering plats from the section, which have been filed at different times over decades and with different degrees of accuracy, and calculating for myself the balance of the section after totaling up the acreage of the platted parcels. This gets difficult because while I have line bearings, I don't feel confident in figuring out angles based on geographic bearings or in working with curves to figure this out by hand.
I am seeking a "shortcut" for the process of calculating balance acreage. Take the parcel below as an example: the lots around it have been platted, so I have data for the boundaries of this parcel, except for the western most line. Given the dimensions I do have, I should be able to calculate the length of that line. I also want to know the acreage of the selected parcel. What is the most efficient way to use ArcMap tools to do this?