Answer:
This is a mixture.
Explanation:
While you can no longer see the salt when it's dissolved, it's still there! It's just in tiny, tiny, invisible to the eye molecules. It's now a mixture of H20 molecules and NaCl molecules in a solution :)
The water doesn't bond to the salt, so it's not a compound.
It's not just one element, it's a mixture of many!
It's not a pure substance since it's NaCl AND H2O.