Understanding Relational Algebra

ๆ•ฐๆฎ่ฎก็ฎ— ๆ•ฐๆฎๅบ“
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1

I am trying to teach myself relational algebra. I came across this one and want to understand exactly what it means.

๐œŽ(๐‘‚๐‘Ÿ๐‘‘๐‘’๐‘Ÿ๐‘ .๐‘œ๐‘‘๐‘Ž๐‘ก๐‘’= ๐‘†โ„Ž๐‘–๐‘๐‘š๐‘’๐‘›๐‘ก.๐‘†โ„Ž๐‘–๐‘๐‘‘๐‘Ž๐‘ก๐‘Ž) (๐‘‚๐‘Ÿ๐‘‘๐‘’๐‘Ÿ๐‘ ร—๐‘†โ„Ž๐‘–๐‘๐‘š๐‘’๐‘›๐‘กร—๐‘‚๐‘Ÿ๐‘‘๐‘’๐‘Ÿ_๐ผ๐‘ก๐‘’๐‘š)
 
โˆง(๐‘‚๐‘Ÿ๐‘‘๐‘’๐‘Ÿ๐‘ .๐‘œ๐‘–๐‘‘= ๐‘†โ„Ž๐‘–๐‘๐‘š๐‘’๐‘›๐‘ก.๐‘‚๐‘–๐‘‘)
 
โ‹€(๐‘‚๐‘Ÿ๐‘‘๐‘’๐‘Ÿ๐‘ .๐‘‚๐‘–๐‘‘=๐‘‚๐‘Ÿ๐‘‘๐‘’๐‘Ÿ๐ผ๐‘ก๐‘’๐‘š.๐‘‚๐‘–๐‘‘)
 
โˆง(๐‘‚๐‘Ÿ๐‘‘๐‘’๐‘Ÿ_๐ผ๐‘ก๐‘’๐‘š.๐‘„๐‘ก๐‘ฆ>30)

Where this part from the first line is shown as superscript:

(๐‘‚๐‘Ÿ๐‘‘๐‘’๐‘Ÿ๐‘ ร—๐‘†โ„Ž๐‘–๐‘๐‘š๐‘’๐‘›๐‘กร—๐‘‚๐‘Ÿ๐‘‘๐‘’๐‘Ÿ_๐ผ๐‘ก๐‘’๐‘š)

Reference - Scaler, Quora