HELP!!!! Dividing one field by another on Looker Studio

Please Please Help!

I am no expert but I have tried EVERYTHING suggested and nothing works and I DEFINITELY have the field names correct and they both will work fine in a table.

I want to divide field Total TG_Event by field Hours of Event and I have tried

CASE
WHEN SUM(`Hours of Event`) = 0 THEN 0
ELSE SUM(`Total TG_Event`) / SUM(`Hours of Event`)
END

And lots of variations and I keep getting told - Syntax error: Expected ")" but got "TG_Event". or similar

Please

Have mercy

Help. I have been trying for ages 

@Expert1 @VoiceOfEveryone @support 

 

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