Resposta :
[tex]\large\boxed{\begin{array}{l}\sf m_{O_3}=3\cdot16=48~g/mol\\\sf 48~g\longrightarrow22,4~L\\\sf 20~g\longrightarrow x\\\sf 48x=22,4\cdot20\\\sf 48x=448\\\sf x=\dfrac{448}{48}\\\sf x=9,33~L\end{array}}[/tex]
[tex]\large\boxed{\begin{array}{l}\sf m_{O_3}=3\cdot16=48~g/mol\\\sf 48~g\longrightarrow22,4~L\\\sf 20~g\longrightarrow x\\\sf 48x=22,4\cdot20\\\sf 48x=448\\\sf x=\dfrac{448}{48}\\\sf x=9,33~L\end{array}}[/tex]