Hurray for Roman numerals!
MDXL = 1,000 + 500 + (50 - 10) = 1,540
this makes the problem much easier. From here you can use our base-ten system to your advantage and find 10% (1/10) by moving the decimal once to the left.
1,540 * .1 = 154
If you wanted to write this in Roman numerals:
100 + 50 + (5 - 1) = CLIV
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