Question

Solve the following:
 $XCII - XV$

Answer 1

Hint: First convert the roman numerals to individual numbers they represent and then do the arithmetic operation over the resultant numbers.
Complete step by step answer:
We will first decipher the number behind the first term.
The conventional symbols for Roman numerals are as follows:
$1 - I,5 - V,10 - X,50 - L,100 - C,500 - D,1000 - M$
Left hand side of each expression is the number and the right hand side equivalent Roman numeral. The rule is that when a symbol appears after a larger symbol we will add it and if it appears before then we will subtract.
Our first term is given by:
$XCII$
Comparing first and second symbols of the above term with the symbols given before, we see that $X$ representing 10 appears before $C$ which represents 100. So we will subtract 10 from 100 to get 90. Then we see $II$ appearing after. So we will add 2 to the above subtraction. Our number behind the first term is 90+2 = 92.
Our second term is given by:
$XV$
Comparing first and last symbols of the above term with the symbols mentioned before, we see that $X$ representing 10 comes before $V$ which represents a smaller number 5. So we will add 5 to 10 and our number behind the second term is 15.
To solve the problem, we have numbers and thus we get
92-15=77
To convert the answer back to Roman numerals we segregate the digits as 70+7.
For 70 we can write, $LXX$ and for 7 we write, $VII$. So our answer is $LXXVII$.
Note: Another rule to keep in mind is to avoid using a single symbol more than three times. You can end up with different symbols for the same number.