In the code num_var = "fifteen", what is the data type of the value?

The Data type is clearly a string because you put it in quotation marks, this tells the computer its a not a integer, but a readable "String"

I think the data type is a string. In computer programming, a string is traditionally a sequence of characters, either as a literal constant or as some kind of variable. The latter may allow its elements to be mutated and the length changed, or it may be fixed (after creation).