The answer to that is found in the way you posed your original question:
Therefore, 'y' is the numerator and 'x' is the denominator.

In this case, with x=$87.00 and y=$828.74:
'x' is 10.5% of 'y' ($87.00/$828.74)*100, which makes it 89.5% less than 'y' ($87.00/$828.74 -1)*100; and
'y' is 953% of 'x' ($828.74/$87.00)*100, which makes it 853% more than 'x' ($828.74/$87.00 -1)*100.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]