[tex]\bf \begin{array}{ccllll}
photos&minutes\\
\textendash\textendash\textendash\textendash\textendash\textendash&\textendash\textendash\textendash\textendash\textendash\textendash\\
28&8\\
21&x
\end{array}\implies \cfrac{28}{21}=\cfrac{8}{x}[/tex]
solve for "x"