L represents 50, and since the I (one) comes before the X (10), that is an subtraction problem. "The Roman numerals were adopted to clarify any confusion that may occur because the NFL ...

So you need to break it down further and think about the Roman numerals you can choose from. 70 can be partitioned into 50 and two 10s. 7 can be partitioned further into 5 and two 1s. These values ...