[tex]\begin{gathered} \text{There are 15 cats.} \\ \text{The ratio of cats to dogs is 3 : 5} \\ \text{If there are d number of dogs, then you have } \\ 15\colon d \\ \text{Therefore,} \\ 3\colon5=15\colon d \\ \frac{3}{5}=\frac{15}{d} \\ \text{Cross multiply and you have;} \\ 3d=5\times15 \\ 3d=75 \\ \text{Divide by 3} \\ \frac{3d}{3}=\frac{75}{3} \\ d=25 \end{gathered}[/tex]
Therefore, you have 25 dogs at the shelter.
