Trouble finding dimension of 2 different heights on a trapezoid

[Anonymous]

I am new to AUTODESK and am not totally sure how to find the dimension depicted in the screenshot included. Any help, please? 

[barthbradley]

When placing your LINEAR Dimensions, Tab-Select the corners until you get a small blue dot.  Pull your Dimension between those  dots.  

[ToanDN]

Use Linear dimension, not Aligned dimension.  Just pick the points, no need to TAB.

[David_W_Koch]

Or you could recognize that is a parallelogram (alternate interior angles are equal - its a geometry thing), and that the offset on right side will be equal to the offset on the left.  To the nearest 1/16", that is 3 3/4".  You could double check that the value shown in the diagram is correct with a little trigonometry:

cos 85° = x/43"

x = 43" * cos 85°

x ≈ 43" * 0.08715574274765817355806427083747

x ≈ 3.7476969381493014629967636460114

But if the task at hand was to actually add a dimension to the figure on the right, then the advice of @barthbradley  and @ToanDN is spot on.