So you’ve found yourself in the ancient world, no paper or pens in sight, and you need to add some three digit numbers together. Lets so say that you’ve been hit on the head and you have no memory of the Hindi numeral system and only know… say… Roman numerals. How do you do it? Start by picking up some pebbles.
So you have just shown that CLVII + CDXCVI = DCLIII.
By the way, if you type an expression in Roman numerals into Google, it will give you the answer in Roman numerals. I just discovered that.
Now you know how to add like an ancient. Way to go!