Okay YolandaQuiles, the first thing we can do is state that that log alone 1/1 or one whole.
To solve the 1/5 cut we write something like....
1/1 - 1/5 - 2/9
To set everything up a little clear we must find a common denominator.
In this case it would be 45, because both 5 and 9 can evenly fit into 45
so the problem would look something like this.....
45/45 - 9/45 - 10/45
now just picking apart the numerator it would look like this
45 - 9 - 10 = 26
So the log would be only be 26/45 of what it used to be