Or you could start at 3 PM, and count your way up one hour at a time, until you get to 12 AM. You should count out 9 hours in total.
An alternative is you could note from 3 PM to 3 AM is a span of 12 hours. Take 3 hours away from 3 AM, and you'll rewind the clock back to 12 AM. So 12-3 = 9. :-)
Or you could start at 3 PM, and count your way up one hour at a time, until you get to 12 AM. You should count out 9 hours in total.
An alternative is you could note from 3 PM to 3 AM is a span of 12 hours. Take 3 hours away from 3 AM, and you'll rewind the clock back to 12 AM. So 12-3 = 9.
