Let x be the fraction that corresponds to the percent of T-shirts sold that were neither small nor large, then:
[tex]x+\frac{3}{20}+\frac{10}{25}=1.[/tex]Adding like terms we get:
[tex]x+\frac{11}{20}=1.[/tex]Subtracting 11/20 from the above equation we get:
[tex]x=1-\frac{11}{20}=\frac{9}{20}\text{.}[/tex]The above fraction as a percentage is
[tex]\frac{9}{20}\times100=45.[/tex]Answer: 45%.
