15:5

It looks like you've provided a ratio or a fraction (15:5). If you want to simplify this ratio, you can divide both numbers by their greatest common divisor (GCD), which is 5 in this case.

15 ÷ 5 = 3
5 ÷ 5 = 1

So, 15:5 simplifies to 3:1.

If you meant something else or if you have a specific question regarding this ratio, please provide more context!