If letter(s) are placed before another letter of greater value, the total value decreases by the amount of the number of lesser value: [e.g., IX = 9, XL = 40, VC = 95]

If letter(s) are placed after another letter of greater value, the total value increases by the amount of the number of lesser value: [e.g., XI = 11, LX = 60, CV = 105]

The total value of repeated letters (1-2 repetitions) is the number of occurences of that letter multiplied by the value of the repeated letter: [e.g., XX = 20, CCC = 300 BUT 40 = XL, (not XXXX)]

The total value of letter(s) with a bar above them is the value of the letters multiplied by 1000: [e.g., IV = 4, IV(need bar) = 4000]