We are told that Julia keeps 255 masks on the wall and 45 on the display case, this means in total the number of masks she has is
[tex]255+45=300\text{masks}[/tex]The number of masks Julia keeps on the wall is 255 masks; therefore, the percentage of fo masks on the wall is
[tex]\frac{255}{300}\times100[/tex][tex]=85.\text{ }[/tex]Hence, Julia keeps 85% of her mask collection on her wall.
