Using summary data in a formula in a report

I have summary fields of Credits and Debits.
AT bottom of report I want to have
Credits - Debits =( Value calculated)

I have the 2 summary fields in place, but how do I write the formula to calculate the value for the difference in the 2 fields?

Thanks

In a summary tile you would have a text display object with the formula

"Credits - Debits = " + pattern(Credits - Debits, "#,.##")

It just comes out like this. + pattern(Credits - Debits, “#,.##”)

I figured it out, my field names are singular, Debit, and they are all caps, DEBIT, plus the object defaults back to literal text, so I am learning. Thanks for your help, your formula worked, once I got the syntax correct.