As Mike already pointed out, units are treated as variables. In case of Your worksheet the "ft" don't cancel because one of them is taken the absolute value from. This can be treated with the "assume" statement.
To avoid those annoying decimals in symboliv results, you have to take care, that all numbers in the expression you evaluate are integers (most of the times hard to accomplish). You can make this in your worksheet by separation of assignment and numeric evaluation, e.g. using "a:=2/3 a=" instead of "a:=2/3=".
If its only the number of digits which disturb you, you can control them using the "float" modifier.
See attached modified sheet
WR
