Help! with relational Algebra

Hi,
I am having a few problems in approaching relational algebra problems, I cannot seem to find a method I should use to tackle them. An example of a problem would be,
Take an SQL example
"INSERT INTO P RELATION {P#:'46', PNAME:'MALCOLM', COLOUR:'Red',
WEIGHT:12.5, CITY:'London'} ;"

Then convert it to a Relational Algebra statement
"P ;= P UNION RELATION { TUPLE{P#:'46',
PNAME:'MALCOLM',COLOUR:'Red',WEIGHT:12.5) ;"

I do not know any way to approach these types of questions (I'm thick). Any help or link to a website explaining how to approach problems like the above would be greatly appreciated

Cheers
Michael Rowlands
michaelrowlands_at_bigfoot.com

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