First, divide the ratio by 2:
[tex]10\colon12\rightarrow\frac{10}{2}\colon\frac{12}{2}\rightarrow5\colon6[/tex]Now, multiply it by two to get the second ratio:
[tex]10\colon12\rightarrow10\cdot2\colon12\cdot2\rightarrow20\colon24[/tex]Thereby, the two ther ratios would be
[tex]\begin{gathered} 5\colon6 \\ \text{and} \\ 20\colon24 \end{gathered}[/tex]