Which number would divide the numerator and the denominator of the firstfraction to yield the second fraction?

Let the fraction to be divided be x.
[tex]\begin{gathered} \frac{10}{12}\div x=\frac{5}{6} \\ \text{Cross multiplying,} \\ x=\frac{5}{6}\times\frac{12}{10}=\frac{2}{2} \end{gathered}[/tex]Therefore, the fractional number which divide the first fraction is 2/2.