Simply this number 15min :3hours​

1 min : 12 min

Step-by-step explanation:

To simplify the given ratio, convert both to the same unit of time.

1 hour = 60 minutes

3 hours = 3 x 60 minutes

             = 180 minutes

So that,

15 min : 3 hours = 15 min : 180 min

divide through by 15 to have;

15 min : 180 min = 1 min : 12 min

Thus the simplified form of the number give is 1 min : 12 min.