3.17: 6-digit numbers divisible by 5 and a combinations equation

A 6-digit number is to be formed using the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. The number cannot start with 0. Each digit can be used at most once. Find how many of these 6-digit numbers are divisible by 5.

The number of combinations of $(n + 1)$ objects taken 13 at a time is equal to 16 times the number of combinations of $n$ objects taken 12 at a time. Find the value of $n$.