Recently i have seen this question and i am unable to find a logic for this.
Here the bike goes with certain speed and after every X minutes the speed decreases. So he increases the speed after every Y minutes. To set the bike in normal condition he have to give K minutes of high speed or 2K minutes of low speed assuming that bike is getting high speed and low speed evenly.
X =4 Y=2 K=7
Here we need to find the total time to get the bike into normal state