Hoe to enter a variablee

I'm confused: can't you do it the same way you wrote the question you posted here?

How to enter a formula may depend on where you are trying to enter it: in a practice problem embedded in an article; in an exercise set, quiz, or unit test; or where?

If this is an accessibility issue, you may want to contact the Accessibility teamhttps://support.khanacademy.org/hc/en-us/articles/360015349472-Can-Khan-Academy-be-used-with-a-screen-reader-or-read-aloud-tools

~ Janice

Hi, John Nivard!

We'd love to have a greater understanding of the issue you're running into. Could you please submit a support request in our Help Center? Here's the link: http://khan.co/KA-support.