The value of 6 in Roman numerals is VI. To write 6 in Roman numerals, we need to represent it as the sum of existing symbols in the Roman numeral system. Since 6 is not part of the seven symbols used in the system (I, V, X, L, C, D, and M), we need to use the existing symbols to represent it. One way to do this is to break 6 into the sum of 5 and 1, which can be written as V + I, resulting in VI. Another way to think about it is to use the additive notation, which states that whenever a bigger letter precedes a smaller letter, the letters are added. Therefore, we can obtain the Roman numeral for 6 by breaking it into the sum of 5 and 1 and writing their respective equivalent Roman letters and combining them, i.e., 6 = 5 + 1 = V + I = VI.