[tex]\bf A = \{ x~|~x \in \mathbb{N}; x\leq 3 \}[/tex]
[tex]\bf x\leq 3\implies x\in \{0,1,2,3\}\implies \green{\boxed{\bf A = \{0,1,2,3\}}}[/tex]
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[tex]\bf B = \{ x~|~x \in \mathbb{N};~ 9\leq x^{2}\leq 36 \}[/tex]
[tex]\bf 9\leq x^{2}\leq 36\Rightarrow 3^{2} \leq x^{2}\leq 6^{2}\Rightarrow 3\leq x\leq 6\Rightarrow x\in\{3,4,5,6\}[/tex]
[tex]\bf x\in \{3,4,5,6\}\implies \blue{\boxed{\bf B = \{3,4,5,6\}}}[/tex]
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[tex]\bf C = \{ x~|~x \in \mathbb{N};~ 3< x\leq 7\}[/tex]
[tex]\bf 3<x\leq 7\Rightarrow x\in\{4,5,6,7\}\Rightarrow\purple{\boxed{\bf C = \{4,5,6,7\}}}[/tex]
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[tex]\bf D = \{ x~|~x \in \mathbb{N};~ 8\leq x^{3}\leq 100 \}[/tex]
[tex]\bf 8\leq x^{3}\leq 100\Rightarrow 2^{3} \leq x^{3}\leq 4^{3}\Rightarrow 2\leq x\leq 4\Rightarrow x\in\{2,3,4\}[/tex]
[tex]\bf x\in \{2,3,4\}\implies \red{\boxed{\bf D = \{2,3,4\}}}[/tex]
[tex]==Salmon==[/tex]
