How would you evaluate 1776 plus 249 in two different ways and 1776 minus 249 in two different ways showing all four calculations in Roman numerals with explanations?

Under today's modern rules now governing the Roman numeral system 249 in Roman numerals is considered to be CCXLIX but the ancient Romans would have probably evaluated the above in any of the following formats:-

A: MDCCLXXVI+ICCL = MMXXV => 1776+(250-1) = 2025

B: MDCCLXXVI+CCXXXXVIIII = MMXXV => 1776+249 = 2025

C: MDCCLXXVI-ICCL = MDXXVII => 1776-(250-1) = 1527

D: MDCCLXXVI-CCXXXXVIIII = MDXXVII => 1776-249 = 1527

QED