This depend on your country and the type of the mail.
All you really need is some stamps and a stamp collecting booklet. Make sure to keep the stamps and booklet in top shape.
Ask at a post office in USA !
This depends on the country of origin, weight of the letter, priority etc; ask at a post office in your country.
That will depend on the value of the stamps you have. If you have one cent stamps you will need 190 of them. If you have ten cent stamps you only need 19.
They are still valid as postage, however, they are only worth 20 cents, which means you would need two of them plus another 4 cents to mail a letter.
it depends on the stamp then you will know how many stamps you will need
3 stamps!
what the price to mail letter to
you need ten stamps actually i don't know
4 stamps
2
maybe 2 0r 3 stamps