Hi Carols,
It appears you are asking:
Hello. Use the response of a previous survey to do a mathematical operation in a new survey. Example: If I have to know how much weight a person lost. I need the weight of the first survey minus the weight of the second survey to know how much weight it lost.
Quick answer, this is not currently possible. Values from a previous survey (different feature record) can not be referenced or queried from within Survey app when collecting a new survey. That being said you could use custom url scheme to pass the values via another app or url link (ie from Collector) into a new usrvye collect. See more information here: Integrate with other apps—Survey123 for ArcGIS | ArcGIS and https://community.esri.com/groups/survey123/blog/2016/07/30/understanding-survey123s-custom-url-sche....
Otherwise you could use a repeat in your survey, and then when editing the parent feature, the related repeat records will be available, and you can use a calculation to retrieve the values from the previous repeat to get the max() value. See how other users have done it here: https://community.esri.com/thread/226403-pulling-data-from-the-previous-repeat#comment-835986
Regards,
Phil.
