About how many young drivers believe that using recreational drugs such as marijuana, cocaine, speed, or ecstasy does not affect their driving?

The number of people who experience the thought process and idea of this, especially teens need to uncover the overall information of this.

No, and it's rather unthinkable to why they would THINK that this does not affect their driving, not even a little. Almost everything has an affect to it, so of course, this does as well have one, and it does on your(or teens, involving as well younger people) driving, as the questions information provides.

Now, answering this question is of the following:

It is said that about 1 in 8 percentile( I believe around 12% it is to be) of younger drivers that believe that recreational drugs( as the examples you provided ) does not affect their driving.

well for some you have to do on your own on a paper but yeah