Answer
21,900 Twinkies
Work Step by Step
To determine how many Twinkies the milkman has eaten you must compute how many days there have been in the last 60 years. At 365 days per year, the number of days in 60 years is:
$365 \times 60 = 21900$
Since the milkman ate one Twinkie per day he has eaten 21,900 Twinkies.
*NOTE - This problem appears to want you to not consider the impact of leap years.