the fraction for this is 15/25 so you find the highest number that will go into both of the numbers, in this case, it would be 5. therefore, you divide 15 and 25 by 5 getting the answer of 3:5 which is the same as 3/5.
i am pretty sure this is how you do it. i am only in yr 8 so ye......
In order to get this answer, you have to figure out how many km 10% is, 0.1125. Then multiply that by the remaining 20% because he already finished 80% of the trail. So, 0.1125 x 20 = 2.25.
