If 1/4 of the shirts are black, and another 1/4 are white, then all the shirts that are "either black or white" is simply an addition of both fractions. This is shown below;
[tex]\begin{gathered} B\text{ or W=}\frac{1}{4}+\frac{1}{4} \\ B\text{ or W=}\frac{1+1}{4} \\ B\text{ or W=}\frac{2}{4} \\ B\text{ or W=}\frac{1}{2} \end{gathered}[/tex]The shirts that are either black or white is 1/2 (one half) of the entire shirts
