Get SUM from a calculation

Hello,

I’m trying to get a total price for a maintenance by summing all amount of work multilplied by work price (grand total)
I was following this topics and video: https://www.youtube.com/watch?v=bZQ4_TTw0kg&t=13s and Summing values in Table but none of them helped me.

• I have database query which outputs all works
• I’m trying to set a value based on a collection {{query_get_expenses.sum('price_expense*amount_expense')}}
  
  

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  In the end I get result 0, but if I’m posting just this code: {{query_get_expenses.sum('price_expense')}} I get sum of all prices

Please help me our because this simple actions took me already 2 days and making me nuts.