How many kilometers he bikes in a week

Let's assess what information we have given to us. 
 
He rides his bike to and from school on Tuesdays, and Thursdays. 
After reading the problem it becomes apparent that the fact that the two days are Tuesday, and Thursday doesn't matter. Instead it tells us how many days out of the week he bikes. 

2 Days biking TO and FROM. 

To and From are two different distances. Now we have to be on alert, because if they give us the total distance (they would likely say something obvious like the total distance is ) we won't have to worry about the two different distances, but if they give us the distances for one trip then will we have to worry about it. (One trip will be indicated by something on the lines of the distance from the school is ..., or one trip is this long...
Keep in mind there are a few more examples for this type, but these should help you identify them)

In this case our distance is given in terms of how far his house is from the school. 

3.62km

Since that is the distance of one trip we need to multiply it by 4, because we have 2 trips every day that we bike, and we bike 2 days out of the week!

3.62km * 4

14.48km is our EXACT answer. So this is the answer the math teacher is looking for. 

The gym teacher wants ABOUT how many kilometers, so we need to round our exact number to the nearest kilometer (km). 

14.48km is the answer you give to the Math Teacher. 
14.00km is the answer you give to the Gym Teacher.