You've got to be more specific.
Are you asking about a 1799 8 reales? Or are you asking about a US 1799 silver dollar? They are two separate coins with vastly different values.
A dollar
how much is a 1799 silver dollar worth
A 1921 Morgan dollar is worth about $25.00
The James Madison Presidential dollar is made of brass, not silver, and is worth one dollar.
One dollar.
A "piece of eight" was the nickname for the Spanish dollar, or real.
There's no silver in it, and it's worth one dollar.
It all goes back to the pirates' "pieces of eight" which referred to the Spanish dollar which was worth eight reils. The Spanish dollar was legal tender in the US until the mid-1800's. At the same time the American dollar was equivalent to 4 quarters. Change for a dollar was often made by breaking or cutting the Spanish dollar into its eight pieces or "bits". By simple math 1 quarter was worth two pieces of eight or two bits. Two bits was 50 cents, six were 75 cents.
how much is a 1924 silver dollar worth
1896 silver dollar is worth how much?
a dollar
A dollar
It depends greatly on the year, early silver dollar proof dollars can be worth several thousand dollars, modern silver dollar proofs of common dates might be worth $20 or so for silver scrap.
how much is a 1799 silver dollar worth
A Washington silver dollar, believe it or not.
As shown on the bottom reverse, it is a "quarter dollar" which is 1/4 of a dollar comprised of 100 cents (25 cents). The slang term "two bits" comes from the Spanish Dollar silver coins, which were each worth 8 reales (pieces of eight)...where one-fourth of that 'dollar' was 2 reales (bits).
One dollar.