Served with child support modification papers.

You have several resources available online.  Try this site to calculatte the child support:  https://www.azcourts.gov/familylaw/Child-Support-Calculator-Information If you want to know the rules used for assigning child support, you can read the Arizzona Child Support Guidelines: https://www.azcourts.gov/familylaw/Child-Support-Guidelines-Review-Archive