$\text{a)}A\cup B=\left\{1,2,3,4,5\right\}\cup \left\{2,4,6,8\right\}=\left\{1,2,3,4,5,6,8\right\}$  

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$\text{b)}A\cap B=\left\{1,2,3,4,5\right\}\cap \left\{2,4,6,8\right\}=\left\{2,4\right\}$  

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$\text{c)}A\text{}B=\left\{1,2,3,4,5\right\}\text{}\left\{2,4,6,8\right\}=\left\{1,3,5\right\}$  

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$\text{d)}B\text{}A=\left\{2,4,6,8\right\}\text{}\left\{1,2,3,4,5\right\}=\left\{6,8\right\}$  

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$\text{e)}B\cap C=\left\{2,4,6,8\right\}\cap \left\{0,5\right\}=\varnothing$  

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$\text{f)}\left(A\cap B\right)\cup C=\left(\left\{1,2,3,4,5\right\}\cap \left\{2,4,6,8\right\}\right)\cup \left\{0,5\right\}=$  

$=\left\{2,4\right\}\cup \left\{0,5\right\}=\left\{0,2,4,5\right\}$  

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$\text{e)}\left(A\text{}B\right)\cap C=\left(\left\{1,2,3,4,5\right\}\text{}\left\{2,4,6,8\right\}\right)\cap \left\{0,5\right\}=$  

$=\left\{1,3,5\right\}\cap \left\{0,5\right\}=\left\{5\right\}$  

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$\text{h)}\left(A\cup C\right)\text{}B=\left(\left\{1,2,3,4,5\right\}\cup \left\{0,5\right\}\right)\text{}\left\{2,4,6,8\right\}=$  

$=\left\{0,1,2,3,4,5\right\}\text{}\left\{2,4,6,8\right\}=\left\{0,1,3,5\right\}$