Hello,

Transform 1.3 into a fraction, ie 13/10.

You have to find the smallest x such as 13x/10 is an integer, that is to say 13 is a multiple of 10.

It's the same as finding the least common multiple between 13 and 10 (Least common multiple - Wikipedia, the free encyclopedia), which will be a multiple of 13 and for 10, and the smallest ! ;-)