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Simplify the following expressions.  Where applicable, identify any restrictions on the variables.

1. \(15\sqrt 5 - 8\sqrt {125} \)
   
   
   
   
2. \(\sqrt {8s^3 } - \sqrt {50s^3 } + \sqrt {108} + \sqrt {147} \)
   
   
   
   
3. \(\sqrt[3]{{54}} + \sqrt[3]{{250}} - \sqrt[3]{2}\)