[tex]2x+45\in\{0,11,22,33,...\}[/tex]
[tex]2x\in\mathbb{N}\Rightarrow2x+45\in\{55,66,77,...\}[/tex]
[tex]2x\in\{10,21,32,...\}[/tex]
[tex]2x~par\Rightarrow2x\in\{10,32,54,...\}[/tex]
[tex]x\in{5,16,27,38,49,...\}[/tex]
[tex]x<40\Rightarrow x\in\{5,16,27,38\}[/tex]
[tex]\boxed{A=\{5,16,27,38\}}[/tex]
