In a word expression such as (width+length)x2 = perimeter of a rectangle, are contractions used in “perimeter”? The UEB manuals don’t seem to cover these types of problems.
Are you doing this in Nemeth or strictly using UEB? If in Nemeth, the begin Nemeth indicator would precede the first paren and follow the word rectangle – and ‘width’, ‘length’, ‘perimeter’ and ‘of’ would be uncontracted. If you are using just UEB, then contractions can be used in all the words.