_ ÷5/15=45/60

$n \div \frac{5}{15}=\frac{45}{60} \\~\\ n\div \frac{5}{15}\times\frac{5}{15} = \frac{45}{60}\times\frac{5}{15} \\~\\ n=\frac{45}{60}\times\frac{5}{15} \\~\\ n=\frac{45\times5}{60\times15} \\~\\ n = \frac{225}{900}$

Then reduce:

$n = \frac14$

So...

$\frac14\div\frac5{15}=\frac{45}{60}$