In the equation there seems to be a typo;

103 - number of ppl in queue, 4 - up to X weeks per person, 2 - number of machines 12 - ??

Maybe you initially wanted to use full months for how long a person can hold an item, but then switched to weeks, and accidently still used number of months to get the number of years?

Anyway, for an imprecise number, you can do with months - 104*1/2/12 ~4.3y.

For more precise result, use seconds, as that's the unit used for the precise length of the year. Year is not 365 days. It's actually longer, quoting Wikipedia for (tropical) year,

> Approximately 365 solar days, 5 hours, 48 minutes, 45 seconds

That gives

  104 * (4 * 7 * 24 * 60 * 60) /2 /(((365 * 24 + 5) * 60 + 48) * 60 + 45)

Which results in 3.986 years. At maximum. Much less than 17!

Edit: getting asterikses * right