[SQL] Converting Relational Algebra to corresponding SQL Query

I am trying to understand how to convert properly from Relational Algebra into SQL queries

I find this is one of the things I struggle to convert between. Would anyone be able to share any tips?

Tables:

Room(_roomId_, numberOfBeds, price)

Guest(_guestId_, homeTown, age)

Reservation(_roomId_, _guestId_, date)


Relational Algebra:

Πprice(ΠroomId(ΠguestId(σage<20)Guest) Natural Join Reservation) Natural Join Room


Query: I managed to deduce the following from part of the statement:

SELECT roomId FROM (SELECT guestID from Guest WHERE age<20) Natural Join Reservation


Am I close?

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