a stamp dated july 4 1976 US first day covers is worth what in mint con.?

Answer 1

It's worth about 50 cents unless the artwork on the envelope is something special. Give it to a kid who collects stamps - or use it to start a stamp collection yourself. Stamps or First Day Covers don't have to be worth a lot of money to be interesting to collect.

Answer 2

If it is on a First Day Cover it isn't in mint condition.
In either case it is worth little. Very few stamps of
the last fifty years have much value. It is still
possible to buy, from stamp dealers, fifty or sixty
year old stamps at face value.