I am a user of Khan Academy on an iPad and sometimes also use it on an Android phone. Unfortunately, the Android phone app doesn't appear to have this capability. If the Android tablet is your platform, you can try looking at the below directions for the iPad to see if this capability is present there. Instead of a cartoon balloon, you may see an icon with CC inside an outline.

Here is how to do it on the iPad (I don't know if iPhone works the same way or even has this capability - worth trying to find out if that's your platform):

1.When you start up a video, pause it.

2. Notice in the bottom right corner of the video screen an icon of two arrows pointing away from each other. Click on this icon. This will hide the transcript. ("Oh, no!" you must be thinking. "At least the transcript was better than nothing." Don't worry, what you need to do next doesn't appear as an option unless the transcript is hidden.)

3. With the video still paused, notice that the icon in the bottom right corner now has the two arrows point toward each other. Then, look to the left of this new icon, where you should see three more icons. The leftmost of these three looks like a cartoon balloon, but more rectangular, with dots and dashes within the rectangle. Click on this one, and you will now see subtitles (also called captions) on the screen! If you missed any portion of the video because you didn't have the subtitles turned on, you can start it over.

4. If for any reason you don't want the subtitles, just click on that cartoon balloon icon to toggle them off. Also, if you return to transcript mode by clicking on the icon with the two arrows pointing toward each other, it will turn off the subtitles (and also not let you see the cartoon balloon icon), but if you exit from transcript mode by clicking on the icon with the two arrows pointing away from each other, you'll see the subtitles again.

5. Subtitles will stay in effect for other videos unless you turn them off. However, if you go into a video other than the one you just watched, you will be in transcript mode and will not see the subtitles unless you click the icon with the two arrows pointing away from each other in the bottom right corner.