I started to use Knime few weeks ago and it´s been being a little challenging.
Lately I´ve been struggling matching two reports, one is general ledger and the other is the trial balance. I would like to matching a sum of rows [from general ledger] with a single row [from trial balance] but I don´t really now which nodes can be useful to this purpose.
Why so? Any specific problems/challenges? If you tell us your background, field you are coming from and what software were you using before maybe we can suggest some materials to help you.
Now to address your current problem. Do you have the sum calculated? When you say matching you mean like joining or comparing or something third? For calculating sum you want to use GroupBy or Math Formula node while for comparing Rule Engine is node to use.
From experience best way to get help from community is to give some example with numbers (dummy data works just fine). For example what is your input and what is your desired output with logic behind it explained if not obvious.